Ketosis pilaris, also known as follicular keratosis, is a common and harmless skin condition that produces dry patches of rough skin with tiny red bumps. It is typically located on the upper arms, cheeks, thighs, or buttocks and does not itch or hurt. The condition tends to worsen in dry winter air or in areas with low humidity. It is caused by the buildup of the keratin protein that is responsible for protecting the skin from harmful substances and infection. The extra keratin blocks the opening of the hair follicles with a keratin plug, and in doing so, it creates a tiny bump on the skin.

It is believed that this condition is hereditary in nature, although it can occur with conditions like atopic dermatitis. Ketosis pilaris will usually clear on its own over time and will likely disappear before the age of thirty. While it cannot be prevented or cured, there are measures that can be taken to improve the appearance of the skin.

Self-care recommendations include moisturizing regularly with a product containing lanolin, glycerin, or petroleum jelly, staying hydrated, limiting bath/shower time to ten minutes or less, using warm instead of hot water to wash, avoiding harsh soaps, and using a humidifier. If using an over-the-counter medicated cream, apply it before moisturizing. It is also a good idea to avoid wearing tight clothing that may create friction by rubbing against the affected area.

When at home care does not seem to help, a dermatologist may prescribe stronger creams that contain alpha hydroxy acid, salicylic acid, lactic acid, or urea to remove dead skin cells. These also work to moisturize and soften the rough skin. Another option is to prescribe creams that contain topical retinoids (derived from Vitamin A) in order to promote cell turnover and prevent hair follicles from becoming plugged. Consistent use of medicated creams may improve the appearance of the skin, but even with treatment, the condition could last for years.