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Keratosis Pilaris

Bumpy Rash on Arms, Thighs, and Cheeks

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Updated April 23, 2010

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Keratosis pilaris is a common bumpy rash that occurs most often on the backs of the arms, front of the thighs, cheeks, and buttocks. The rash can occur at any age, but it's often at its worst during the teen years. Almost 50% of teenagers have keratosis pilaris and 80% of teenage girls have it. It tends to run in families, but a specific gene that causes keratosis pilaris hasn't been discovered.

Cause of Keratosis Pilaris

Keratosis pilaris is caused by a buildup of keratin that plugs the pores, causing the bottom of the pore to get larger. This causes irritation around the pore and often traps hair in the pore. The pressure inside the pore can thin out the lining and shrink the sebaceous gland.

Keratosis Pilaris Appearance

Keratosis pilaris looks like tiny, hard bumps similar to when you have goosebumps. Sometimes the skin around the bumps is red. It can occur anywhere on the body except the palms of your hands and the soles of your feet, but it occurs most often on the:
  • Back of the arms
  • Front of the thighs
  • Buttocks
  • Cheeks

Diagnosis of Keratosis Pilaris

Keratosis pilaris is diagnosed clinically, meaning based on the typical features of the rash. If there is any question about the diagnosis, a doctor might do a skin biopsy to be sure, but these rarely need to be done.

Keratosis Pilaris Treatment

Unfortunately, there are no treatments that cure keratosis pilaris. However, there are medications and other measures you can take to make it less noticeable or bothersome. On the bright side, keratosis pilaris usually starts improving on its own in the late teen years.

Because the rash gets worse with dry skin, following the eczema skin care guidelines would help improve skin hydration.

Prescription medications that contain exfoliants like lactic acid, salicylic acid, and urea can be helpful. Examples of these medications include:

  • Lac-Hydrin
  • Vanamide
  • Keralac

If the rash is very irritated, the doctor may prescribe a topical steroid to use for a short time until the irritation improves. Retin-A might be an option if everything else fails but it's variably effective and often too irritating.

Sources:

Habif, Thomas. “Atopic Dermatitis.” Clinical Dermatology, 4th Ed. Philadelphia: Mosby, 2004. 116-7.

Hwang, S, and RA Schwartz. “Keratosis pilaris: a common follicular hyperkeratosis.” Cutis. 82(2008): 177-80.

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