What causes keratosis pilaris?

What is happening inside the bumps?

A hair follicle is the opening in the skin where a hair grows. In keratosis pilaris, keratin collects in the upper part of that opening instead of shedding normally. Dead skin cells plug many follicles, creating patches that feel rough and dry. The bumps can resemble tiny pimples, but the material forming them is keratin.234

The usual sites are the upper arms, thighs and bottom, although other areas can be affected. Bumps are usually painless and can match your skin colour, look red on white skin or darker on brown or black skin. Some patches itch. Keratosis pilaris is harmless and is not infectious: you cannot catch it or pass it to someone else.1

Who is more likely to get keratosis pilaris?

People of all ages and races develop keratosis pilaris. It commonly starts before age two or during the teenage years, and women are slightly more likely to have it. The following increase the likelihood of developing it; they are risk factors, not a checklist that diagnoses the bumps.4

• Close blood relatives with keratosis pilaris.
• Dry skin or eczema, also called atopic dermatitis.
• Ichthyosis vulgaris, a condition that causes very dry skin.
• Asthma or hay fever.
• Excess body weight.

Genetics appear to contribute. Keratosis pilaris has been linked with changes in filaggrin, a protein involved in the skin barrier. A genetic association does not explain every case, and the exact reason keratin collects remains uncertain.3

What causes keratosis pilaris in adults?

Adults develop the same keratin plugs as children. Keratosis pilaris can persist from childhood or become more obvious in adulthood. Hormones can trigger a flare around puberty, and cases that begin during the teenage years often clear by the mid twenties. That is not a deadline: some people continue to have bumps through adult life.34

One specific medicine linked with keratosis pilaris is vemurafenib, a targeted treatment for melanoma that has spread. Rough bumps usually appear within the first eight weeks and can worsen as the dose increases. If this applies to you, discuss the bumps with your treating dermatologist; ammonium lactate cream or lotion is one treatment they can direct.4

Why does it get worse in winter?

Keratosis pilaris often becomes more prominent in winter, likely because the air contains less moisture. Dryness makes the condition worse, while summer can bring improvement. Hot bathing, drying perfumed products and harsh scrubbing can aggravate the skin, so the useful target is dryness rather than removing every bump by force.13

Does keratosis pilaris mean a vitamin deficiency?

Another condition called phrynoderma can cause similar follicular bumps because of nutritional deficiencies. If the diagnosis is uncertain, a clinician can examine the skin rather than treating its appearance as a vitamin test.23

How can you reduce the roughness?

Treatment is optional because ordinary keratosis pilaris is harmless. If the bumps bother you, moisturizing and gentle care can improve their appearance. Moisturizers can soften the bumps, so a plain cream has a job even without an elaborate origin story.2

1. 1Wash with a mild, unperfumed bathing product and cool or lukewarm water. Keep showers to 15 minutes or less.
2. 2If you exfoliate, use a washcloth gently rather than a harsh scrub. Do not scratch, pick or rub the bumps.
3. 3Apply moisturizer after bathing while the skin is still damp. Use moisturizer daily, and reapply several times through the day for dry skin.
4. 4For persistent roughness, consider a moisturizing cream containing urea, lactic acid, salicylic acid or another alpha hydroxy acid. These ingredients moisturize or loosen the scale stuck inside follicles. A pharmacist can help you choose.

Topical retinoids, vitamin A related medicines applied to skin, are another treatment option. Medicated creams can irritate skin when overused, so more product is not a better treatment. Persistent itch or redness can need a different approach from rough texture; clinicians sometimes use short courses of steroid cream for itch or light treatments for redness.23

How long does keratosis pilaris last?

Many people have keratosis pilaris for years, and it can eventually clear by itself. There is no cure, although it often improves during adult life. Treatment aims to improve texture and appearance rather than deliver a cure, a distinction that tends to get less space on the jar.13

When should you get the bumps checked?

Speak to a pharmacist if home care is not helping and the bumps bother you, or if the skin becomes itchy or inflamed. Painful bumps are not typical of keratosis pilaris and deserve assessment. A doctor can usually identify keratosis pilaris by examining the skin; testing is not usually necessary. Other conditions can look similar, so get an uncertain diagnosis checked before adding stronger treatments.12