Skin conditions.

Acne is the most common skin condition in the world. Around 85% of teenagers get it, and plenty of adults deal with it too.

Eczema (atopic dermatitis) is a long-term, flare-prone kind of itchy, inflamed skin. It affects roughly 10 to 20% of kids and 5 to 10% of adults.

"Fungal acne" is a misleading name. It's really Malassezia folliculitis, an irritation of the hair follicles caused by an overgrowth of a yeast that normally lives on everyone's skin.

Melasma is a long-term kind of discoloration that shows up as matching brown or grey patches on sun-exposed parts of the face. It's far more common in women and in medium-to-deep skin tones, and it often appears or worsens with pregnancy, birth control, or hormone therapy (the so-called "mask of pregnancy").

Perioral dermatitis is a stubborn rash of tiny red bumps around the mouth, nose, or eyes. It's almost always set off by skincare itself, most often steroid creams (including over-the-counter hydrocortisone), heavy face creams, some toothpastes, and fragranced products.

Rosacea is a long-term condition that causes facial redness and flushing, and sometimes bumps and pimple-like spots. It affects about 5% of adults and most often shows up in fair-skinned people between 30 and 60.

Seborrheic dermatitis is a common, flare-prone rash that appears in oily areas like the scalp, eyebrows, sides of the nose, ears, and chest. It happens when a normal skin yeast (Malassezia) feeds on your skin's oils and your skin reacts to the byproducts with inflammation.

Photoaging is the damage that builds up in skin after years of sun and daylight exposure. It shows up as fine lines and deeper wrinkles, uneven color and dark spots, visible blood vessels, and a loss of firmness.