How Do You Diagnose Rosacea From Pictures of a Rash?

Dermatologists diagnose rosacea after examining the skin and eyes, followed by asking the patient a series of questions, according to the American Academy of Dermatology. No specific tests determine if someone has rosacea, but dermatologists may confirm a root cause with special tests performed on the skin, notes MedicineNet. A skin biopsy, skin scrape, skin culture or a blood test can help eliminate other causes of facial blushing and redness that occur with rosacea.

People can find pictures of four subtypes of rosacea through the website of the National Rosacea Society. These photos provide some guidance for how the condition appears on a person's face. Subtype one includes facial redness, while subtype two involves bumps and pimples. Subtype three includes skin thickening around the nose, and subtype four involves eye irritation.

A skin scrape may confirm the presence of Demodex mites on the surface of the skin, states MedicineNet. Demodex mites may cause certain types of rosacea. A skin culture could reveal a staph or herpes infection as opposed to rosacea. Blood tests can confirm lupus, dermatomyositis or some other autoimmune disease that may cause skin inflammation similar to rosacea. Dermatologists remove a piece of skin as part of a skin biopsy, and then doctors examine these cells under a microscope. In addition to rosacea, a skin biopsy can identify rashes, skin cancer and moles.