Acne-Like Bumps (Sio Pod): Causes, How Many Days They Last, and the Right Medicine for Each Type

3 days ago

17 min read

“Sio pod” (in English usually acne aestivalis or heat rash, depending on context) is not a diagnosis in dermatology textbooks. It is the term Thai people use for “small bumps of similar size that appear together in clusters on the face or body, mostly without a pus head and impossible to squeeze out”. When a doctor actually examines them, the same appearance turns out to come from at least 7 completely different conditions, and each one needs a different medicine.

This is why so many people cannot get rid of their acne-like bumps. It is not that the medicine is bad; it is that the medicine they are using belongs to a different condition. The clearest example is fungal acne (Malassezia folliculitis), which needs an antifungal but is often treated with the antibiotics used for inflamed acne. The result is that it flares more the longer they are used, because the antibiotic suppresses the resident bacteria that were keeping the yeast in check.

This article separates the 7 types of acne-like bumps seen in the clinic, with generic drug names, strengths, how to use them, how long before you should see results, and a timeline of how many days each type takes to clear.

How acne-like bumps differ from ordinary acne: 5 signs you can check yourself

Acne (acne vulgaris) comes from blocked follicles combined with oil and the bacterium Cutibacterium acnes. What people call acne-like bumps mostly does not arise from that mechanism at all. In practice there are 5 points that tell them apart.

Is the size uniform? Real acne comes in mixed sizes on the same face: blackheads, whiteheads, red bumps and pustules. Acne-like bumps are almost all about the same size, roughly 1–3 millimetres.
Do they appear together or one by one? Acne-like bumps usually flare up together in clusters within 1–3 days, while real acne appears one spot at a time over several weeks.
Is there a head, or can it be squeezed out? Most acne-like bumps cannot be squeezed out and have no oily core, unlike clogged pores, which release a white or black plug.
Is it itchy? Real acne tends to be more painful than itchy, while many kinds of acne-like bumps are clearly itchy, especially with sweat or heat.
Is it linked to heat, sweat or a new cream? Acne-like bumps often have a trigger you can put a date on, such as after exercise, after wearing a helmet, or after switching sunscreen.

Type 1: Fungal acne (Malassezia / Pityrosporum folliculitis)

This is the most common type among people who say “I have treated my acne for ages and it will not go away”. It is caused by overgrowth of the resident yeast Malassezia in the hair follicles.

Appearance Small red bumps or tiny pustules, almost all the same size at 1–2 millimetres, packed in patches on the forehead, hairline, temples, neck, chest and upper back, with no blackheads or whiteheads mixed in.
Causes Damp, stuffy conditions, sweat, hot weather, long-term antibiotic use, heavy creams or oils, hair products running onto the forehead, a weakened immune system, and steroid use.
Severity / urgency Not dangerous, but chronic and very likely to come back if treatment is not continued after it clears.
When to see a doctor When there is clear itching together with bumps that are all the same size, or when you have used acne treatment for 6–8 weeks and it is unchanged or worse.

The single most important point is that fungal acne does not respond to antibiotics, whether topical or oral, and prolonged antibiotic use can genuinely make it worse, because it reduces the resident bacteria that compete with the yeast.

Type 2: Heat rash (Miliaria)

It is caused by blocked sweat ducts, so sweat leaks into the layers of the skin instead of reaching the surface. It has nothing to do with being dirty and nothing to do with hair follicles.

Appearance It is divided by how deep the blockage is. The superficial type (miliaria crystallina) looks like very small clear blisters, like dew drops, not red, not itchy, and easily broken. The middle type (miliaria rubra), the most common, is small red bumps that itch or sting like pinpricks. The deep type (miliaria profunda) is raised skin-coloured bumps without obvious redness, seen in people who have had repeated episodes.
Causes Hot, humid weather, heavy sweating that cannot evaporate, thick tight clothing, long bed rest, high fever, or heavy products that seal the skin.
Severity / urgency Usually mild and clears on its own once you are out of the heat, but if it covers the whole body and sweat cannot escape, there may be a risk of overheating.
When to see a doctor When it covers the whole body, comes with a fever, has obvious pus, or keeps coming back and affects sleep.

The key point is that heat rash needs neither an antifungal nor an antibiotic, and covering it with cooling powder or a heavy cream often makes the blockage worse. You can read how to tell the 4 types apart in What causes heat rash, and how to tell it from an allergic rash.

Type 3: Keratosis pilaris

It is an inherited condition in which keratin plugs the openings of the hair follicles. It affects about 30–50% of the general population and is more common in teenagers.

Appearance Small firm bumps, skin-coloured or slightly red, rough like sandpaper when touched, appearing evenly on the outer upper arms, front of the thighs, cheeks and buttocks. Usually not itchy, or only slightly.
Causes Genetics together with dry skin. It is usually worse in cold weather and better in hot weather, and is linked to eczema and chronic dry skin.
Severity / urgency Not dangerous at all. It is a matter of appearance and how the skin feels, and it usually improves gradually on its own with age.
When to see a doctor When you want to reduce the roughness, or when there is persistent redness on the cheeks as well, which may be an inflamed type that needs different treatment.

More details are in What causes keratosis pilaris, and how far can it really be cleared.

Type 4: Closed comedones (whiteheads)

This is the only one in this group that is “real acne” by the medical definition, but people often call it acne-like bumps because the spots are small and appear in sheets.

Appearance Raised skin-coloured or cloudy white bumps, 1–2 millimetres, not red and not itchy, most visible under angled light or when you run a hand over them, thick on the forehead, cheeks and jaw. Some can be squeezed out as a white oily plug.
Causes Dead skin cells mixed with oil plug the pore. Often triggered by heavy cosmetics, sunscreens that clog pores, not cleansing thoroughly after make-up, or hormones.
Severity / urgency Not dangerous, but it is the starting point of inflamed acne and dark marks if left alone or picked.
When to see a doctor When painful red bumps start to appear among them, or when you have used a topical medicine yourself and the skin is so red and peeling that you cannot continue.

Details on telling open from closed comedones are in What causes clogged pores, and how to tell blackheads from whiteheads.

Type 5: Sun-related acne-like bumps (Acne aestivalis / Mallorca acne)

This is the type that best matches the English term “acne aestivalis”, and it often arrives with the season.

Appearance Small raised red bumps of equal size, with no pus head and no blackheads, on the cheeks, temples, upper arms, shoulders and upper chest, the areas exposed to sun and sweat at the same time. It starts about 1–3 days after strong sun or a beach holiday.
Causes A reaction of the hair follicles to UV radiation together with ingredients in sunscreens or oily moisturisers, especially textures containing oils and certain emulsifiers.
Severity / urgency Not dangerous, and it usually clears by itself within 2–8 weeks once the strong-sun period is over.
When to see a doctor When it comes back every summer, or when it leaves red or dark marks lasting more than 3 months.

Type 6: Perioral dermatitis, the one most often overlooked

This type matters especially because wrong treatment clearly makes it worse, and it is the type people most often treat themselves with steroid cream.

Appearance Small red bumps and tiny pustules on a faintly red base around the mouth, around the nose and around the eyes. The classic sign is a band of normal skin about 3–5 millimetres wide right around the lips that has no rash at all. It usually stings more than it itches, and the skin peels in fine flakes.
Causes Continuous use of steroid cream on the face, steroid nasal sprays or asthma inhalers, some fluoride toothpaste formulas, and sunscreens or heavy moisturisers.
Severity / urgency Not dangerous to the body, but treatment takes several weeks to several months, and it always gets worse temporarily while the steroid is being stopped.
When to see a doctor As soon as you suspect it, because treatment needs a planned stop of the steroid, and you should not stop it on your own without other medicine to cover you.

Type 7: Irritation from skincare (Irritant / contact dermatitis)

This type is becoming more common with the fruit acids and retinoids now widely sold.

Appearance Small red bumps scattered over red, dry, peeling skin, usually itchy or burning. The edge of the rash often matches exactly where the product was applied. It starts within 1–14 days of beginning something new.
Causes Fruit acids, retinoids, fragrance, preservatives, alcohol, or layering several products until the skin barrier breaks down.
Severity / urgency It clears once the trigger is stopped, but if you keep using it the skin becomes more and more sensitive and harder to tell apart from other conditions.
When to see a doctor When you have stopped every product for 2 weeks and it is still not better, or when there is swelling or oozing.

Telling acne-like bumps apart by location on the face

Location is a practical clue and is the first thing a doctor looks at.

Forehead and hairline Think of fungal acne first, especially if you use shampoo, conditioner or hair serum, wear a cap or helmet, or have a fringe over the forehead.
Both cheeks, symmetrical Think of closed comedones from cosmetics, sun-related acne-like bumps, and the cheek form of keratosis pilaris in teenagers.
Nose and nasolabial folds with greasy scale, think of seborrhoeic dermatitis, not acne-like bumps.
Around the mouth and nose with a normal band of skin next to the lips, think of steroid-related perioral dermatitis.
Chin, jaw and neck that flare with the monthly cycle, think of hormonal acne, explained in Hormonal acne: which jaw and chin pattern is it really.
Neck, chest and upper back that itch after sweating, think of fungal acne and heat rash first. See Back acne: what causes it, and how to tell real acne from fungal acne.

Telling acne-like bumps apart by itch: itchy versus not itchy points to different groups

The question “is it itchy?” rules out half the options in one sentence.

Clearly itchy, especially with sweat or heat points to fungal acne, red-bump heat rash and irritant rash.
Stinging more than itching points to perioral dermatitis and irritant rash from fruit acids or retinoids.
Not itchy at all points to closed comedones, keratosis pilaris and sun-related acne-like bumps.
Painful when pressed is not acne-like bumps but inflamed acne or bacterial folliculitis, explained in What causes folliculitis, and how to clear it without recurrence.

Comparison table of the 7 types in 30 seconds

Fungal acne Same-size bumps 1–2 mm · itchy · forehead, neck, back · antifungal · better in 2–4 weeks
Heat rash Clear or small red bumps · itchy or stinging · sweaty areas · just keep cool and dry · clears in 2 days to 2 weeks
Keratosis pilaris Firm rough bumps · not itchy or slightly · upper arms, thighs, cheeks · keratolytic cream · results in 8–12 weeks
Closed comedones Cloudy white bumps with a plug when squeezed · not itchy · forehead, cheeks, jaw · topical retinoid · results in 8–12 weeks
Sun-related acne-like bumps Same-size red bumps · not itchy or slightly · cheeks, shoulders, chest · avoid sun and change the cream texture · clears in 2–8 weeks
Perioral dermatitis Red bumps on a red base, sparing the lip border · stinging · around mouth, nose, eyes · stop steroid under a doctor’s plan · 4–8 weeks or more
Irritant rash Red bumps on red, peeling skin · stinging or itchy · exactly where applied · stop the trigger · better in 1–2 weeks

How many days do acne-like bumps last? The real timeline for each type

The question people ask most is how many days it takes. The honest answer is that it depends on the type, and the numbers differ a lot.

Heat rash, clear-blister type clears fastest, about 24 hours to 3 days after leaving the heat and drying the skin.
Heat rash, red-bump type about 3–14 days. If you stay in the same hot, humid conditions it can return straight away.
Irritant rash from skincare starts to improve within 3–7 days of stopping the trigger and settles in about 2–4 weeks.
Fungal acne Itching usually improves within 1–2 weeks and the bumps flatten clearly at 2–4 weeks, but treatment must continue at a lower frequency, otherwise it very often comes back within 1–3 months.
Sun-related acne-like bumps 2–8 weeks, depending on avoiding the sun.
Closed comedones You need to wait 8–12 weeks for a real result, and the first 2–6 weeks often look worse because the blocked material is pushed to the surface.
Keratosis pilaris 8–12 weeks before the skin feels softer, and this is control, not a permanent cure.
Perioral dermatitis At least 4–8 weeks, and it gets temporarily worse for 1–2 weeks while the steroid is stopped.

If you have treated the right type for the full period above and see no improvement at all, it means the diagnosis is probably not right, not that the dose needs to go up.

Medicines for each type of acne-like bumps: drug names, strengths and how long to use them

This section is written the way a doctor would explain it to a patient in the consulting room, to show what treatment matched to the type looks like. Choosing the drug, the dose and adjusting it is always the job of the examining doctor.

Fungal acne (Malassezia folliculitis)

Ketoconazole 2% shampoo, used as a face or body wash: lather over the whole affected area, leave for 5 minutes, then rinse off, once a day for 2–4 weeks, then reduce to 1–2 times a week for at least another 1–3 months to prevent recurrence. The 5-minute wait is where people most often go wrong, because rinsing off straight away leaves the drug almost ineffective.
Selenium sulfide 2.5% or zinc pyrithione 1–2% can be used in place of it in the same way.
Ketoconazole 2% cream or clotrimazole 1% cream, applied thinly 1–2 times a day for 2–4 weeks, for localised patches on the face.
For widespread or frequently recurring cases, or when topical treatment is not enough, a doctor may consider an oral antifungal such as itraconazole or fluconazole as a short course. Co-medications, liver disease and pregnancy must always be checked first, so these are prescription-only medicines.
What tells you it is or is not working Itching should drop clearly within 1–2 weeks. If the number of bumps has not fallen at all after 4 weeks, go back and review the diagnosis rather than increasing the strength of the medicine.

Heat rash (Miliaria)

The heart of treatment is reducing heat and drying the skin, not medicine. Move somewhere cool, wear thin cotton, and pat the skin completely dry after bathing.
Calamine lotion can be applied as needed to relieve itching.
Hydrocortisone 0.5–1% cream, applied thinly 1–2 times a day for no more than 3–7 days, only for the red-bump type that itches a lot, and not to be used continuously on the face for long because of the risk of perioral dermatitis.
What tells you it is or is not working It should improve within a few days once the skin is dry and cool. If there is no improvement at all, it is not heat rash.

Keratosis pilaris

Urea 10–20% cream, or lactic acid 10–12%, applied 1–2 times a day after bathing.
Salicylic acid 2–5% is an alternative for people who cannot tolerate urea.
A topical retinoid such as adapalene 0.1% gel or tretinoin 0.025–0.05% cream, applied at bedtime every other night at first, then increased to every night.
It must be applied continuously for 8–12 weeks before results can be judged, and when you stop, the skin becomes rough again within a few months, because this is control, not a permanent cure.

Closed comedones

Adapalene 0.1% gel, applied thinly over the whole area at bedtime, once a night, or tretinoin 0.025–0.05% cream.
Benzoyl peroxide 2.5–5% is used as an add-on when red bumps are mixed in.
Azelaic acid 15–20% is an option for sensitive skin and helps with dark marks.
During the first 2–6 weeks of adjustment the skin often looks worse and peels. Reduce the frequency temporarily and add a moisturiser alongside rather than stopping the medicine altogether. The real result is judged at 8–12 weeks.

Sun-related acne-like bumps (Acne aestivalis)

Reducing sun exposure and switching to a light, non-comedogenic sunscreen is the main treatment.
Azelaic acid 15–20% or a low-strength topical retinoid helps the bumps settle faster and reduces recurrence next season.

Perioral dermatitis

The first and most important step is to stop steroid cream on the face, planned together with a doctor, because the first 1–2 weeks always get temporarily worse.
Metronidazole 0.75% gel or cream, applied 1–2 times a day, or erythromycin 2% gel, for 4–8 weeks.
In more severe cases a doctor may use oral doxycycline as a course of several weeks. Here the antibiotic works by reducing inflammation; it is not used because this is an infection.

Irritant rash from skincare

Stop every product that is not essential, leaving only a gentle cleanser, a simple moisturiser and sunscreen.
Hydrocortisone 0.5–1% cream, short term, no more than 5–7 days on the face, when the stinging and redness are severe.
Reintroduce products one at a time, at least 2 weeks apart, so you can identify the culprit.

Why it flares more the more you treat it: the 4 most common mistakes

Using antibiotics on fungal acne This is the number one reason for “treatment that will not work”, because antibiotics do not kill yeast, and reducing the resident bacteria lets the yeast grow better.
Applying steroid cream to the face because the redness settles quickly It really does improve within a few days, but when you stop it flares back harder than before, and it is the starting point of perioral dermatitis.
Scrubbing or washing the face more often because it seems dirty This breaks down the skin barrier and makes every type in this article worse, especially heat rash and irritant rash.
Changing several products within the same week This makes it impossible to tell which one helped and which one is the trigger.

What not to do with acne-like bumps

Do not squeeze, pick or prick them with a needle, because most acne-like bumps have no core to remove. What you get instead is red and dark marks.
Do not apply cooling powder or heavy cream over sweaty areas, because it increases blockage.
Do not take leftover oral antibiotics from a previous course on your own.
Do not use steroid cream on the face without a doctor’s prescription.
Do not use hot compresses or steam your face during a flare, because heat is the main trigger for many of these types.

How to prevent acne-like bumps from coming back

Deal with sweat within 30 minutes Shower, or at least wipe down and change clothes straight after exercise, because lingering sweat is a shared factor in both fungal acne and heat rash.
Wash hair products off the forehead and hairline every night, especially if you have a fringe over the forehead.
Choose light-textured sunscreens and moisturisers labelled non-comedogenic and use only as much as you need.
Regularly clean things that touch your face Pillowcases once or twice a week, and helmet straps and cloth masks after every use.
Keep treatment going at a lower frequency if you have had fungal acne, for example using the medicated shampoo as a wash 1–2 times a week in hot weather, because yeast is a resident organism that cannot be permanently eliminated.
Avoid antibiotics for longer than necessary because they are a direct trigger for fungal acne.

What dermatologists use to tell the types of acne-like bumps apart

History of triggers and timeline Did it flare all at once or appear gradually, and is it linked to sun, sweat, medicines or a new product?
Examination with magnification and angled light to see whether blackheads or whiteheads are mixed in, which immediately separates real acne from the non-acne group.
A skin scraping tested with KOH solution, with a result in about 10–15 minutes, which helps confirm fungal acne when many round yeast cells are seen.
A culture when bacterial infection is suspected or there has been no response to treatment.
A skin biopsy, used very rarely, only when the rash is unusual or chronic with no known cause.

Signs that you should see a dermatologist

You have treated it yourself for 4–6 weeks and it is no better at all or is worse.
Bumps appear very fast within 1–2 days together with fever, pain, swelling or tenderness.
There is pus, oozing, or spreading red, warm skin around the bumps.
It began within 1–3 weeks of starting a new medicine, so a drug rash must be ruled out first.
Bumps appear on only one side of the body with burning pain, so shingles must be ruled out.
You have used steroid cream on the face for a long time and it flares every time you stop.
It is starting to leave dark marks, red marks or permanent scars.

In short

Acne-like bumps are not a single disease but a shared appearance of at least 7 conditions, each treated with a different medicine.
The two questions that separate them fastest are “is it itchy?” and “where is it?”.
Bumps that are all the same size, itchy, on the forehead, neck and back: think of fungal acne first, and fungal acne does not respond to antibiotics.
Bumps that are not itchy and squeeze out a white plug: think of closed comedones, which need 8–12 weeks for results.
Clearing times vary a lot, from 1–3 days for clear-blister heat rash to 8–12 weeks for clogged pores and keratosis pilaris.
The first thing to do is stop any steroid cream you have put on your face yourself, stop any product you have just started, and have a dermatologist tell the type apart before starting medicine, rather than trying medicines one after another.

Frequently asked questions

How do I treat acne-like bumps so they clear?

You need to identify the type first and then choose the medicine, because each type of acne-like bumps uses a different drug group. For fungal acne, use an antifungal such as ketoconazole 2% shampoo as a wash, left on for 5 minutes before rinsing, once a day for 2–4 weeks. For heat rash, simply cooling and drying the skin lets it clear on its own in 2 days to 2 weeks. For closed comedones you need a topical retinoid and 8–12 weeks to see results. Trying medicines one by one without knowing the type often damages the skin and drags the problem out. Choosing the drug and dose should be under a doctor’s care.

What should I use for acne-like bumps?

If you have not yet seen a doctor, what is safe and helps with almost every type is to reduce heat and sweat sitting on the skin, wash the face with a gentle product twice a day without scrubbing, use a light, non-comedogenic moisturiser, and stop any product you started within the past month. What you should not use on your own is steroid cream on the face or leftover oral antibiotics, because both clearly make fungal acne and perioral dermatitis worse.

What causes acne-like bumps on the forehead?

The forehead and hairline are where fungal acne is found most often, because they have dense oil glands, sweat that lingers under the hair, and hair products that run down. Next most common are clogged pores from sunscreen or foundation that was not fully washed off, and friction from caps, helmets or headbands. A helpful clue: if the bumps are almost all the same size and itch when you sweat, it is probably fungal acne, but if they do not itch and squeeze out a white plug, it is probably closed comedones.

What causes acne-like bumps on the cheeks?

There are several causes on the cheeks. The common ones are closed comedones from cosmetics and sunscreen, sun-related acne-like bumps in people who have just had strong sun, and irritant rash from skincare, where the edge of the rash matches the area where the product was applied. Some teenagers have keratosis pilaris on the cheeks, which feels rough and has usually been present since childhood. If it is symmetrical on both sides and appeared together after a change of product, suspect the product first.

Is there really a fast way to treat acne-like bumps?

There is no method that clears acne-like bumps in a single day for every type. The fastest thing is to stop the trigger: leave the heat, dry the skin, stop any product you just started, and stop steroid cream. In heat rash this may show results within 24–72 hours, but fungal acne needs at least 1–2 weeks and clogged pores need 8–12 weeks. Methods claiming instant results are often steroids, which really do settle quickly but make the rash flare back harder than before.

What do acne-like bumps look like, and how do they differ from clogged pores?

Acne-like bumps is a catch-all term for small bumps of similar size that appear together in clusters, mostly cannot be squeezed out, and in many types itch. Clogged pores are a single clear-cut condition: follicles blocked by skin cells and oil, appearing as cloudy white bumps or blackheads that do not itch and can be squeezed out as an oily plug. In practice, closed comedones are one of the 7 causes people lump together as acne-like bumps, and the only one in this group that counts as real acne by the medical definition.

References

Rubenstein RM, Malerich SA. Malassezia (Pityrosporum) folliculitis. Journal of Clinical and Aesthetic Dermatology
American Academy of Dermatology. Acne-like breakouts could be folliculitis (aad.org)
DermNet NZ. Malassezia folliculitis (dermnetnz.org)
DermNet NZ. Miliaria (dermnetnz.org)
DermNet NZ. Keratosis pilaris (dermnetnz.org)
DermNet NZ. Perioral dermatitis (dermnetnz.org)

Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed 10 September 2026