Diagnosing Skin Problems

Medically Reviewed by Stephanie S. Gardner, MD on July 26, 2021

Doctors can diagnose some skin problems by how they look. For other problems, they will use skin tests.

Your doctor will first examine you and ask about your medical history. They may check to see if your skin problems may be caused by psoriasis or other chronic conditions.

Skin tests can help to diagnose  allergies, infections, and other problems affecting the skin. They're are also used to tell the difference between malignant (cancerous) cells and benign (noncancerous) cells.

The most common skin tests include:

  • Patch testing: Patch tests are used to diagnose skin allergies. Allergens (substances that a person may be allergic to) are applied to the skin on the back with adhesive patches and left for a period of time. The skin is then examined for any reaction.
  • Skin biopsy: Skin biopsies are used to diagnose skin cancer or benign skin disorders. During a skin biopsy, skin is removed (after a local anesthetic is applied) and is taken to a laboratory for analysis. Skin may be removed with a scalpel, razor blade, or a cylindrical punch biopsy tool. Stitches may be used to close the wound. 
  • Culture: A culture is a test that is done to identify the microorganism (bacteria, fungus, or virus) that is causing an infection. Skin (surface scrapings, biopsies, contents of pus bumps and blisters), hair, or nails may be cultured.

Dermoscopy (a noninvasive method using a handheld device that enables dermatologists to better see the lesion), confocal imagers, and tape stripping to look at genetic material are other diagnostic techniques.

Show Sources


Bruce E. Strober, MD, PhD, associate director of Dermatopharmacology, Department of Dermatology, New York University School of Medicine; co-director of the Psoriasis and Psoriatic Arthritis Center.

Jeffrey M. Weinberg, MD, director of the Clinical Research Center, St. Luke's-Roosevelt Hospital Center, New York City; assistant clinical professor of dermatology, Columbia University College of Physicians and Surgeons.

National Institute of Arthritis and Musculoskeletal and Skin Diseases.

American Academy of Dermatology.


National Psoriasis Foundation.

Abel, E. "Dermatology III: Psoriasis," ACP Medicine, April, 2005.

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