Inflammatory Acne: Causes, Which Medicines to Use and How to Avoid Scars
Inflammatory acne is an acne lesion in which a follicle that was already clogged becomes inflamed, turning into a raised red bump that hurts when pressed. In severe cases it becomes a pustule, a hard lump under the skin, or a cyst. It differs from a clogged-pore comedone, which is a white or black-headed bump that is neither red nor painful.
What makes inflammatory acne matter more than other types is that inflammation reaching the dermis can permanently damage the collagen structure, which is how acne scars form. So the goal of treatment is not just to flatten the visible bump quickly but to stop the inflammation as early as possible so that no scar is left behind.
This article breaks inflammatory acne into the subtypes doctors actually use to make decisions, giving generic drug names, strengths, how long treatment takes, and signs that a medicine is or is not working.
What is inflammatory acne, and how does it differ from clogged pores?
All acne starts from the same point, a clogged follicle. What separates a comedone from inflammatory acne is whether inflammation has started yet.
Comedone — a cloudy white bump or one with a black head, 1–2 millimeters, not red, not painful, with a plug of oil coming out when squeezed.
Inflammatory acne — a red raised bump that hurts when pressed, from 2 millimeters to more than 1 centimeter, with or without a pus head.
The most common misunderstanding — thinking that 'acne with pus' is acne infected from the outside. In fact the pus in acne is white blood cells the body sends to deal with the Cutibacterium acnes already living in the follicle. It is not an infection that always needs antibiotics by mouth.
Most people have both types mixed together, and treatment that really works has to handle both. If you treat only the inflamed spots without fixing the underlying blockage, the acne comes back in the same places within a few weeks. For details on the underlying cause, read What causes clogged pores (comedonal acne).
What causes inflammatory acne — four mechanisms at once
Inflammatory acne does not have a single cause. It comes from four mechanisms working in sequence, so each treatment targets a different one.
The oil glands produce more oil, stimulated by androgen hormones, which rise in adolescence, 5–7 days before a period, and in PCOS.
Skin cells lining the follicle shed abnormally, causing a blockage at the follicle opening. This is the step that retinoid drugs address.
Cutibacterium acnes multiplies in the clogged, low-oxygen follicle, producing substances that stimulate the immune system.
The immune system responds by sending white blood cells and inflammatory substances, causing redness, swelling and pain, and if the follicle wall ruptures, the inflammation spreads into the dermis.
Common, correctable triggers include hormonal changes, stress and lack of sleep, heavy cosmetics and sunscreens, friction from masks or helmets, and certain drugs such as steroids, some hormones and lithium.
How many types of inflammatory acne are there, and why tell them apart
Inflammatory acne is divided by depth and appearance into 4 main types. Telling them apart is not academic; it directly determines whether you need a topical alone, an oral drug as well, or a procedure, and it indicates how likely a scar is.
A simple rule: the deeper and larger the lesion, the sooner and stronger the treatment must be, because the risk of acne scars rises with depth.
Type 1 · Papule (red bump without a head)
Appearance: a red raised bump 2–5 millimeters, with no white or yellow pus head, mildly to moderately painful when pressed, with a still-smooth surface.
Cause: a clogged follicle begins to inflame but pus has not yet gathered. This is the earliest stage of inflammatory acne.
Severity and urgency: low. Most settle on their own in 5–10 days and respond well to topicals. They leave no pit if not picked, but can leave redness for 4–12 weeks.
When to see a doctor: when there are more than 10–20 at once, or the count has not gone down after 8 weeks of continuous topical use.
Type 2 · Pustule (acne with a pus head)
Appearance: a red bump with a white or yellow head in the center, 2–5 millimeters, clearly more painful than a plain red bump.
Cause: the inflammation progresses until white blood cells gather into pus in the superficial skin. This pus is immune cells, not dirt from outside.
Severity and urgency: moderate. It settles on its own in 7–14 days, but it is the type people squeeze most, and squeezing incorrectly is the number one cause of dark marks and shallow pits on the face.
When to see a doctor: when they appear in a dense cluster in one area, or appear very quickly within 1–2 days with itching, which may not be true acne but fungal folliculitis.
Type 3 · Nodule (hard lump under the skin)
Appearance: a firm raised lump larger than 5 millimeters, felt deep under the skin, with red or darkened skin on top, no head, very painful when pressed, and sometimes throbbing even when untouched.
Cause: the follicle wall ruptures deep down, letting oil, keratin and bacteria leak into the dermis, so the body builds inflammation around it as a lump.
Severity and urgency: high. It can last 2–6 weeks and carries a risk of permanent acne scars from the very first lesion. This is the group in which topicals alone are often not enough.
When to see a doctor: as soon as the first one appears. Do not wait and see, because an anti-inflammatory injection in the first few days clearly reduces both the pain and the chance of scarring. More detail is in the article What causes nodular acne, and can you squeeze it?
Type 4 · Cyst
Appearance: a large raised lump from more than 5 millimeters to more than 1 centimeter, softer than a hard nodule, feeling as if there is fluid inside, dark red and very painful, sometimes bursting on its own with blood-tinged pus.
Cause: the same mechanism as a nodule, but with pus and inflammatory material accumulating in a deep pocket. It often occurs together with many severe lesions at once and is linked to genetics more than to behavior.
Severity and urgency: the highest. It can last several weeks to a month, leaves a scar in almost every case, and is a clear indication for oral medication.
When to see a doctor: immediately. Delayed treatment in this group costs you acne pits that are harder to fix and take many times longer to treat than the acne itself.
Five conditions that look like inflammatory acne but are not acne
Many cases of inflammatory acne that 'will not go away' come from a wrong diagnosis at the start, because these conditions look very much like acne but need different drugs.
Fungal folliculitis (Malassezia folliculitis) — red bumps or pustules of nearly identical size, 1–2 millimeters, densely packed on the forehead, hairline, chest and back, clearly itchy, with no mixed blackheads or whiteheads. It needs antifungal treatment, and antibiotics will make it worse.
Perioral dermatitis — small red bumps on a red base around the mouth, with a normal band of skin 3–5 millimeters wide next to the lips that has no rash at all. It stings more than it itches and often follows steroid cream used on the face.
Rosacea — background facial redness with visible tiny blood vessels, and red bumps and pustules scattered over the center of the face, with no comedones at all, and flushing on exposure to sun, spicy food or hot things.
Bacterial folliculitis — pustules with a hair in the center, usually appearing after shaving, waxing or wearing tight clothes while sweating.
Hidradenitis suppurativa — repeated painful lumps in the armpits, groin and under the breasts that come and go, with openings and discharge. It is not acne and needs a different treatment approach.
The deciding point used in the examination room is this: if there are no comedones at all, suspect that it is not acne.
Why you should not squeeze inflammatory acne — how scars form
Squeezing inflammatory acne pushes the contents of the follicle in two directions. Some come out through the opening, but the rest is pushed deeper and ruptures the follicle wall further. The results are:
The inflammation spreads wider, from one lesion into a red, swollen surrounding area.
The depth of collagen damage increases, which determines whether a pit is left.
Post-inflammatory dark marks become darker and last longer, especially in Asian skin, which easily produces pigment in response to inflammation. Dark marks from squeezed acne usually take 3–12 months to fade, compared with 4–12 weeks for acne left to settle on its own.
The only exception is extraction of a clogged-pore comedone by a doctor or trained person using sterile instruments, on a lesion with a clearly open head, not squeezing inflammatory acne that is still red and has no head.
Assess severity before choosing medicine
Dermatologists use both the number and the type of lesions to grade acne, because this determines whether to start with a topical or to use an oral drug from the beginning.
Mild — mostly comedones, with fewer than 10–20 red bumps or pustules in total, and no deep lumps. Start with topicals alone.
Moderate — roughly 20–100 red bumps and pustules in total, or spread over both the face and the body. Usually needs a topical together with an oral drug.
Severe — more than 5 nodules or cysts, acne spreading to the back and chest, or scars already beginning to show. This is an indication for an oral retinoid.
A criterion that matters as much as the count is whether scars have already formed. If so, treat it as severe and treat actively right away without waiting for the count to be reached.
Topical for inflammatory acne no. 1 · Benzoyl peroxide
Generic name: benzoyl peroxide
Strengths and forms: 2.5%, 5% and 10% as a gel, cream or face wash foam. The 2.5% strength works no differently from 10% in any meaningful way but irritates much less, so it is the most suitable starting point.
How and how long: apply a thin layer only to the affected areas, once a day at bedtime for the first 1–2 weeks, then increase to twice a day if the skin tolerates it. Assess the result at 6–8 weeks.
What shows it is working: fewer new red bumps per week, and existing lesions settling faster.
What to know: it dries and peels the skin in the first 1–2 weeks, which is normal, and it permanently bleaches fabric, so use white pillowcases and towels. The advantage that keeps this drug a mainstay is that C. acnes does not become resistant to it, so it can be used together with an antibiotic to reduce resistance.
Topical for inflammatory acne no. 2 · Topical retinoids
Generic names: adapalene, tretinoin, tazarotene
Strengths and forms: adapalene 0.1% gel is the least irritating and is available in Thailand · tretinoin 0.025–0.05% cream or gel is stronger but more irritating and breaks down in light
How and how long: apply across the whole acne-prone area, not just on individual spots, once each night on completely dry skin. Start with 2–3 nights a week for the first 2 weeks and then increase to every night. Assess the result at 12 weeks, not 4 weeks.
What shows it is working: the clogged pores you can feel on the forehead and cheeks become smoother, and fewer new inflammatory lesions appear.
What to know: in the first 2–6 weeks you may see a temporary flare of acne as clogged pores under the skin are pushed up, which is a normal response and not an allergy. Sunscreen is needed every day, and do not use it in pregnancy or when planning pregnancy.
Topical for inflammatory acne no. 3 · Topical antibiotics
Generic names: clindamycin and erythromycin
Strengths and forms: clindamycin 1% gel, lotion or solution · erythromycin 2% gel
How and how long: apply 1–2 times a day for 6–12 weeks. Do not use alone; always use together with benzoyl peroxide or a retinoid.
What shows it is working: clearly fewer pustules within 4–6 weeks.
What to know: the reason not to use them alone is antibiotic resistance in C. acnes, which can develop within a few months and make this class ineffective in both topical and oral forms. Using it together with benzoyl peroxide clearly reduces this problem.
Topical for inflammatory acne no. 4 · Azelaic acid and options for sensitive skin
Generic names: azelaic acid, salicylic acid, dibenzoylmethylurea
Strengths and forms: azelaic acid 15–20% cream or gel · salicylic acid 0.5–2% in face washes and toners
How and how long: apply azelaic acid twice a day. Assess the result at 8–12 weeks.
What shows it is working: both the red bumps and the post-acne dark marks fade together.
What to know: azelaic acid reduces blockage, fights bacteria and reduces pigment, so it is especially useful for people whose main problem is post-acne dark marks, and it is one of the options that can be used in pregnancy once a doctor has assessed it. Salicylic acid is weaker and suits an add-on role, not a main one.
Oral medicine group 1 · Oral antibiotics
Generic names: doxycycline, minocycline; in children under 8 years and in pregnant women, erythromycin is used instead.
Commonly used doses: doxycycline 100 milligrams once or twice a day, or a low dose of 40–50 milligrams a day for an anti-inflammatory effect.
Duration: 3–4 months, then stop. Do not take it continuously for longer, because that increases resistance without increasing the treatment benefit. It must always be used together with a topical, and when the oral drug is stopped a topical must continue to keep acne under control.
What shows it is working: new inflammatory bumps fall by at least half within 6–8 weeks. If there is no reduction at all at 8 weeks, review whether it is really acne instead of increasing the dose.
What to know: doxycycline clearly makes the skin more sensitive to sunlight, and should be taken with a full glass of water while sitting or standing, not lying down within 30 minutes, to reduce esophageal irritation. Do not use it in pregnancy or in young children.
Oral medicine group 2 · Isotretinoin
Generic name: isotretinoin, an oral vitamin A derivative.
Indications: severe inflammatory acne with nodules and cysts · moderate acne that has not responded to topicals plus a full course of oral antibiotics · acne that has already left scars · acne that returns quickly every time treatment is stopped.
Dose and duration: start at about 0.25–0.5 milligrams per kilogram of body weight per day, then adjust according to response and side effects. It is generally given continuously for 4–8 months, and a total cumulative dose of about 120–150 milligrams per kilogram is often targeted to reduce the chance of relapse.
What shows it is working: new acne stops appearing and oiliness clearly decreases within 4–8 weeks, with a temporary flare possible in the first month.
What to know: this drug causes severe birth defects, so strict contraception and scheduled pregnancy tests are required throughout treatment and for 1 month after stopping. Side effects that always occur are dry, cracked lips and dry skin. Liver function and blood lipid levels must be checked before starting and during treatment, and it must not be combined with tetracycline-class drugs. This drug is prescribed and monitored by a doctor only.
Oral medicine group 3 · Hormonal treatment in women
Who it suits: women whose acne is mainly on the jawline, chin and around the mouth, flares with the menstrual cycle, with irregular periods, excess hair growth or hormonal hair thinning, or acne that first appears after age 25.
Generic names used: combined hormonal contraceptive pills containing a progestin with anti-androgen activity, and spironolactone, which is often used at roughly 50–100 milligrams a day for this indication.
Duration: it must be used continuously for at least 3 months before the result can be judged, and the full effect is usually seen at 6 months.
What to know: spironolactone must not be used in pregnancy, may cause irregular periods and high potassium levels in some people, so underlying conditions and other medicines must always be assessed first. Contraceptive pills are contraindicated in heavy smokers, people with a history of blood clots, or migraine with aura. Details on recognizing this type of acne are in the article Hormonal acne on the jawline and chin: how to tell.
Procedures that help, not replace medicine
Procedures have a clear place in inflammatory acne, but none can replace the main medicines.
Intralesional anti-inflammatory injection with diluted steroid into a nodule or cyst makes it settle and stop hurting within 24–72 hours. It is the best way to reduce the chance of a pit in a single nodule. It must be done by a doctor because too high a concentration can make the skin sink in.
Extraction of comedones with sterile instruments is used for open and closed comedones, not for lesions that are actively inflamed.
Chemical peels such as salicylic acid or fruit acids help with comedones and dark marks, and must be spaced apart from retinoids.
Lasers and light therapy play a supporting role in some people and are more useful in the later scar-correction stage, such as fractional laser and carbon dioxide laser for acne pits, or vascular laser for lingering redness. The choice of type must be assessed individually by a doctor.
How many weeks until you see results, and what shows a medicine is not working
Wrong expectations are the reason people stop treatment too early and then the acne returns.
Weeks 1–2 — do not expect results yet. The skin is often dry and peeling from topicals.
Weeks 2–6 — there may be a temporary flare from retinoids. This is not a sign the medicine is not working.
Weeks 6–8 — you should see clearly fewer new inflammatory bumps. This is the first real assessment point.
Week 12 — the point of full assessment for topical retinoids.
Months 3–6 — the period for assessing hormonal treatment and oral medicines.
Signs that the treatment plan needs to be reviewed, not just waited out: using topicals correctly for a full 8–12 weeks and the count has not gone down at all · deep lumps or cysts starting to appear during treatment · pits or scar marks starting to show · or very itchy bumps, which suggest fungal folliculitis rather than acne.
How to treat it without leaving scars
Acne pits form when collagen in the dermis is destroyed. Once formed, they do not come back on their own with topicals, so the prevention principles are few and every one of them is practical.
Treat early. The risk of scarring is related to how long the inflammation continues, not just its severity.
Do not squeeze, pick or dig. Especially lesions that are red and have no head yet.
Deal with deep lumps from the first one by seeing a doctor for an anti-inflammatory injection instead of waiting for it to settle on its own.
Keep using medicine until the full period is done. Do not stop as soon as things look better, because new acne recurring in the same spot is what makes pits deeper.
Use sunscreen every day. It does not prevent pits, but it stops post-acne dark marks from becoming darker and lasting longer.
Treat scars after acne is under control. Correcting pits while new inflammatory acne keeps appearing gives results that do not last.
How red marks, dark marks and acne pits differ
After acne settles, what remains is of three kinds, and the outlook for each is very different.
Red marks (post-inflammatory erythema) — flat pink to red marks that blanch when pressed, caused by lingering dilated capillaries. They usually fade on their own in 4–12 weeks up to 6 months.
Dark marks (post-inflammatory hyperpigmentation) — flat brown to gray marks that do not blanch when pressed, caused by pigment overproduced during inflammation. Common in Asian skin, they fade more slowly than red marks and can take 3–12 months.
Acne pits (atrophic scars) — indentations where you can feel the skin is not smooth, caused by lost collagen. They do not fade on their own over time and need to be corrected with procedures.
The key difference is that the first two are a matter of time and sun protection, while the third is a matter of lost structure. To learn how to tell them apart and how they are treated, read What causes acne marks and Can acne pits really be filled in?
Daily skin care during treatment for inflammatory acne
Skin care does not treat acne, but it lets you keep using your medicines without the skin breaking down, which is the variable that makes many people give up halfway.
Wash your face twice a day with a gentle product, without scrubbing or using scrub beads. Washing more often than this irritates the skin so it can no longer tolerate the topicals.
Use a light, non-comedogenic moisturizer every day, especially when using a retinoid or benzoyl peroxide.
Use sunscreen every morning, SPF 30 or higher, in a light texture, because both retinoids and doxycycline make the skin sensitive to light.
Change pillowcases often and wash your face after exercise, within 30 minutes when possible.
Stop any product you started within the last month if acne flares up with several lesions at once in exactly the area where it was applied.
Do food, milk and sugar really affect inflammatory acne?
The current evidence points the same way, but the effect is smaller than people assume.
High-glycemic-index foods such as sugary drinks, desserts and refined starches have evidence linking them to acne severity. Cutting them down helps some people.
Cow's milk, especially skim milk, has observational data linking it to acne. Yogurt and cheese are less clear.
Whey protein has been reported to make acne flare in some people, especially those whose acne appears within 1–3 months of starting it.
Chocolate and fried food: the evidence is not strong enough to conclude they are a direct cause.
The practical conclusion is that food is a contributing factor, not the main one. Changing diet alone without medicine is not enough for moderate or worse inflammatory acne.
When to see a dermatologist
A hard lump under the skin or a cyst, even just one
You are starting to see indentations or scars
You have used topicals correctly and continuously for 8–12 weeks with no improvement
Acne is spreading to the chest, back and upper arms
Acne first appears after age 25, or comes with irregular periods, excess hair growth or hair thinning
Bumps appear quickly within 1–2 days together with fever, pain, spreading swelling or oozing
Acne is clearly affecting your confidence and daily life
The last item is no less valid a reason than the others. The psychological impact of acne is an accepted indication for treatment in clinical practice.
In short
Inflammatory acne is acne in which a clogged follicle has become inflamed. It divides into red bumps, pustules, hard nodules and cysts, and the deeper it is, the higher the risk of acne pits.
If there are no comedones at all, suspect it may not be acne, for example fungal folliculitis, perioral dermatitis or rosacea, which need different drugs.
Mild acne starts with topicals: benzoyl peroxide 2.5–5% together with adapalene 0.1%, assessed at 8–12 weeks.
Moderate or worse usually needs oral medicine, such as doxycycline 100 milligrams a day for 3–4 months together with topicals, while nodules and cysts are an indication for isotretinoin.
Do not squeeze lesions that are red and have no head, because it is the shortest path to dark marks and pits.
What to do today: if you have a deep lump, already have scars, or have used topicals for a full 8–12 weeks without improvement, see a dermatologist for assessment and a plan using the right class of medicine.
Frequently asked questions
How do I get rid of inflammatory acne?
First work out the level. If there are no more than 10–20 red bumps and pustules, start with a topical combination of benzoyl peroxide 2.5–5% and adapalene 0.1% gel, applied continuously and assessed at 8–12 weeks. If there are hard nodules, cysts, or more lesions than that, oral medicine is usually needed as well, such as doxycycline 100 milligrams a day as a 3–4 month course. What stops acne from ever going away is changing medicines every 2 weeks and using an antibiotic alone, which makes bacteria resistant. The choice and dose of medicine should be under a doctor's care.
How can I make inflammatory acne go down quickly?
The fastest safe step is a cold compress for 10–15 minutes, 2–3 times a day, to reduce swelling and pain, together with dabbing on a thin layer of benzoyl peroxide and never touching that lesion again. For a very painful nodule or cyst, an anti-inflammatory injection by a doctor makes it settle within 24–72 hours, which is the only method that is truly fast and leaves no damage. Methods to avoid are squeezing and dabbing on toothpaste or alcohol, which spread the inflammation and leave dark marks for longer.
Which acne medicine works fastest?
For lesions with a pus head, benzoyl peroxide 2.5–5% shows results fastest, within a few days, because it acts directly against bacteria. Clindamycin 1% helps reduce pustules but must be used with benzoyl peroxide to reduce resistance. For red bumps with no head, azelaic acid 15–20% helps with both inflammation and dark marks. Adapalene 0.1% is not a drug that makes existing lesions settle faster; it is the one that reduces new lesions and needs to be assessed at 12 weeks.
Why did inflammatory acne suddenly appear?
The most common cause is hormonal change, such as 5–7 days before a period, or ongoing stress and lack of sleep. Next is a new product started within the past month, including skin care, sunscreen, cosmetics and hair products that run onto the forehead. Then comes friction from masks, helmets or resting the chin on the hand, and certain drugs such as steroids and some hormones. If many bumps appear at once and are clearly itchy, also consider fungal folliculitis, because it is treated differently.
Can inflammatory acne be left alone?
Small red bumps and pustules in small numbers can be left to settle on their own in 7–14 days, without leaving a pit if they are not squeezed. But hard nodules and cysts should not be left, because they can last several weeks and keep destroying collagen until a permanent pit remains in almost every case. A simple deciding rule: if you can feel a deep lump, it throbs, or it keeps recurring in the same place, do not wait, because the price of waiting is a scar that is many times harder to fix than treating the acne.
Does taking zinc really reduce acne?
Some studies have found that oral zinc helps reduce inflammatory acne somewhat, but the overall effect is clearly smaller than oral antibiotics, and the data are not consistent enough to recommend it as a main treatment. It is reasonable as an add-on for people who cannot use antibiotics or who are trying to avoid oral drugs. A caution is that high doses often cause nausea and stomach pain, and taking it continuously for a long time may interfere with copper absorption, so talk to a doctor before using it regularly instead of buying high doses to take on your own.
The information in this article is for education and is not a diagnosis or an individual treatment order. The choice of drug, dose and duration must be assessed and prescribed by a doctor.
Warning: acne treatments and skin procedures carry a risk of not working as expected, and may cause harm or side effects. Results vary from person to person. Treatment should always be assessed and carried out by a doctor.
See all skin condition articles at All skin condition articles
Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed September 11, 2026
Comments