DEAR READER: Dapsone is commonly prescribed to treat dermatitis, herpetiformis (a skin condition that commonly appears on the elbows and knees), acne, infection and more.

Lichen planus appears in the mouth or on the skin as an itchy, swollen rash. While its exact cause is unknown, it is thought to be related to an allergic or immune reaction, from exposure to specific medications, chemical substances that include gold rings or necklaces, hepatitis C and other causes.

Diagnosis is made through visual examination or skin-lesion biopsy. Once made, treatment might include antihistamines, lidocaine mouthwashes, topical corticosteroids, creams, ointments or ultraviolet-light therapy. The condition may last for an extended period, but is generally not harmful.

Methemoglobinemia is a blood disorder that occurs when an abnormal amount of a type of hemoglobin builds up in the blood. There are two inherited forms. The first is passed on by both parents, who don’t ordinarily have the condition themselves but carry a gene that causes it. The second form is known as hemoglobin M disease, caused by a defect in the hemoglobin molecule itself. In this case, only one parent passes on the abnormal gene.

The acquired type is more common than the inherited form and occurs following exposure to anesthetics, specific antibiotics and nitrates that are used as additives to prevent meat from spoiling.

Symptoms present with shortness of breath, headache, fatigue and a blue tint to the skin. The treatment of choice is methylene blue. Alternatives include exchange transfusions and hyperbaric-oxygen therapy.

From your brief explanation, my guess is that you were prescribed dapsone because of lichen planus. While you may have been allergic to the medication, I don’t believe it was the cause of your lichen planus but was the treatment of choice because of it. If I have misinterpreted your letter, we can take it up again at a later date.

To provide related information, I am sending you a copy of my Health Report “Blood — Donations and Disorders.” Other readers who would like a copy should send a self-addressed stamped No. 10 envelope and a $2 check or money order made payable to Newsletter and mailed to Newsletter, P.O. Box 167, Wickliffe, OH 44092-0167. Be sure to mention the title or print an order form off my website at www.AskDrGottMD.com.

I am writing to you as a last resort for help. I have read on the computer that it is short-lived, but may come back. I have had it for three years now, and while it doesn’t always cause pain, it is annoying. Can you offer any suggestions or aid?

I once sent away for pills that were supposed to rid me of it, but they did nothing to help and they were expensive — $65 for a 30-day supply. I think they were some kind of herb.

DEAR READER: Perhaps your “last resort” will solve the problem. The precise cause of lichen planus remains unknown. As you are aware, it is thought to be related to an autoimmune disease or allergy and presents with mouth and skin lesions. The mouth lesions can be painful, may increase in size and are located on the sides of the tongue, inside the cheek, and occasionally on the gums. Skin lesions have distinct borders, can develop blisters or ulcers, are shiny or scaly in appearance, and are symmetrical and itchy. Risks include exposure to gold, some diuretics and antibiotics, other medications and hepatitis C. A physician makes the diagnosis through visual examination.

Related symptoms are ridges in finger and toenails, a metallic taste in the mouth, hair loss and dry mouth.
Treatment includes apple-cider vinegar or lidocaine mouthwashes, antihistamines, cyclosporin or other immune-suppressing medications, topical or oral corticosteroids, topical ointments or creams and ultraviolet-light therapy.

The prognosis is good in that lichen planus isn’t generally harmful and should get better with treatment. It commonly clears up within 18 months, but can come and go for years. One possible complication that can occur is oral cancer. Therefore, it is extremely important you remain in contact with your dentist for examination on a regular basis.

DEAR READER: The exact cause for this annoying condition is unknown, but it is thought to be related to allergies from exposure to antibiotics, other medications, hepatitis C, iodides, diuretics, chemical substances such as compounds in gold rings or bracelets, and more.

Mild symptoms may not require any treatment. More complex cases generally respond to antihistamines, topical or oral corticosteroids, ointments or creams, lidocaine mouthwashes and medications to suppress the immune system. Lichen planus may respond to treatment over time but may also wax and wane for years. Be sure to see your physician or dentist for regular exams, since long-standing mouth ulcers can develop into oral cancer.