Light Patches on Skin: Fungus or Something Else?

Light patches usually announce themselves in summer: the skin around them tans, they do not, and suddenly the chest or back looks map-patterned. The good news is that the most common cause is a harmless, treatable yeast, and the serious causes look different enough that a few checks at home tell you which conversation to have.

The yeast that will not tan#

Tinea versicolor, also called pityriasis versicolor, is an overgrowth of Malassezia, a yeast that lives on virtually all human skin. In heat, humidity and sweat it multiplies and produces acids that dial down pigment production beneath it. The patches are typically on the chest, back, shoulders, neck and upper arms, finely flaky if scratched gently, sometimes mildly itchy, and lighter than surrounding skin, though on pale skin they can read as pink or tan instead.

Two reassurances people need to hear: it is not contagious, and it says nothing about cleanliness. Some skins simply host an enthusiastic strain, which is also why it tends to come back in hot months.

Treatment is pleasingly simple: an antifungal shampoo used as a body wash, ketoconazole or selenium sulfide, left on five to ten minutes before rinsing, daily for one to two weeks. The color takes months to even out after the yeast is dead, catching up as the skin sees sun; that lag is expected, not failure. A once-monthly preventive wash through summer keeps repeats away.

The lookalikes#

Vitiligo is the one people fear. It is an autoimmune loss of pigment cells: patches are chalk-white rather than merely lighter, smooth with no flake, often symmetrical, and favor the face around the mouth and eyes, the hands, and friction areas. It is not dangerous in itself, but it deserves a doctor visit, both for confirmation and because treatment works best early.

Pityriasis alba explains most pale patches on children's cheeks and upper arms: mildly scaly, linked to dry skin and eczema, and it fades over months with plain moisturizer. Post-inflammatory hypopigmentation is the pale ghost any skin inflammation can leave behind, from eczema to a healed graze, and it also fades. And ringworm, despite the name another fungus, makes a scaly ring with a raised, advancing edge and a clearing center; the same antifungal cream family treats it.

Sorting yours in one minute#

Flaky, on the trunk, worse-looking after sun: versicolor territory, and the wash is worth trying. Chalk-white, smooth, around mouth, eyes or hands: see a doctor about vitiligo. A scaly expanding ring: antifungal cream, and a doctor if it multiplies. A child's slightly scaly pale cheeks: moisturizer and patience. Numb, growing fast, or just not behaving: get it looked at.

If a cream and a month have not moved things, or you are simply unsure what you are looking at, our dermatologist photo review settles it for $39 without a waiting room, and the free symptom diary tracks whether a patch is changing.