Your doctor will likely be able to determine whether you have seborrheic dermatitis by examining your skin. He or she may scrape off skin cells for examination (biopsy) to rule out conditions with symptoms similar to seborrheic dermatitis, including:
- Psoriasis. This disorder also causes dandruff and red skin covered with flakes and scales. With psoriasis, usually you'll have more scales, and they'll be silvery white.
- Atopic dermatitis (eczema). This skin reaction causes itchy, inflamed skin in the folds of the elbows, on the backs of the knees or on the front of the neck. It often recurs.
- Tinea versicolor. This rash appears on the trunk but usually isn't red like seborrheic dermatitis patches.
- Rosacea. This condition usually occurs on the face and has very little scaliness.