Dermatologist Jerome Z. Litt, M.D., of Beachwood, Ohio, learned about rare and unique reactions documented in the medical literature while writing and updating the Drug Eruption Reference Manual yearly for the past 15 years.

As a result, Dr. Litt has just published a consumer book, Curious, Odd, Rare, and Abnormal Reactions to Medications(Barricade Books, 2009). And he says that dermatologists are likely to see patients with these conditions, given that such drugs as commonly prescribed antibiotics trigger them.

"As dermatologists, we not only care for dermatologic ailments, but we are also confronted with other, somewhat related issues that are frequently asked of us," says Dr. Litt, who practices in Beachwood and is assistant professor of dermatology at Case Western Reserve University School of Medicine.

"For example, who does not hear the question: ‘Why is my fingernail turning darker?’" he asks.

Melanonychia is a common clinical occurrence and a normal finding in the nails of dark-skinned people, occurring in more than 70 percent of blacks older than age 20, according to Dr. Litt. The condition can also signal more serious problems, such as renal disease or melanoma.

However, according to Dr. Litt, drugs have been reported, in rare instances, to cause melanonychia. These include chemotherapeutic drugs and several antibiotics, such as fluconazole (Diflucan, Pfizer) and methotrexate, among others.

Here are some other questions that dermatologists may hear, with the corresponding drugs to consider as the culprits:

Why is my psoriasis getting worse? — Drug reactions can worsen or trigger psoriasis. Dr. Litt says the very biologic response modifiers adalimumab (Humira, Abbott), infliximab (Remicade, Centocor), alefacept (Amevive, Astellas) and etanercept (Enbrel, Amgen and Wyeth) that dermatologists prescribe to treat psoriasis patients could be aggravating the condition. Other medications that can worsen or trigger psoriasis include antimalarials hydroxychloroquine (Plaquenil, Sabofi-Aventis), beta blockers, lithium and ACE inhibitors.

"If you know what medication is causing the reaction, you have to stop the drug and try a different drug. Lithium, for example, is a very common cause of psoriasis; so, you might have to give some patients a different kind of antipsychotic," Dr. Litt says.

Why are my eyelashes growing longer? — Trichomegaly is usually congenital but can occur in several disorders, including dermatomyositis, uveitis, lupus erythematosus, AIDS, malnutrition, hypothyroidism and breast cancer, according to Dr. Litt.

Drugs that can cause trichomegaly include topical glaucoma medications bimatoprost (Lumigan, Allergan), latanoprost (Xalatan, Pfizer) and travoprost (Travatan, Alcon), as well as phenytoin (Dilantin, Prizer), cetirizine (Zyrtec, McNeil) and some AIDS drugs.

Why is my tongue black and hairy-looking? — Lingua villosa nigra occurs as a result of overgrown bacteria and, sometimes, yeast that live in the mouth.

"Almost all antibiotics can cause it, as well as antipsychotic and antianxiety drugs, such as olanzapine (Zyprexa, Lilly), imipramine (Tofranil, Novartis) and mirtazapine (Remeron, Schering-Plough)," he says.

Why is my ringing in the ears becoming louder? — While patients might not visit dermatologists for tinnitus, some of the drugs that dermatologists and other doctors commonly prescribe can cause or worsen ear ringing.

Aspirin is a common culprit, as well as many antibiotics, including clarithromycin (Biaxin, Abbott), chloramphenicol (Chloromycetin, Pfizer), methotrexate and some antidepressants, such as fluoxetine (Prozac, Lilly) and bupropion (Wellbutrin, GlaxoSmithKline).

Why am I getting more canker sores in my mouth? — For the most part, the true cause of aphthous stomatitis remains a mystery, but some believe that canker sores could be due to drug allergies, according to Dr. Litt. Medications that could cause a canker sore reaction include imiquimod (Aldara, Graceway) and NSAIDs.

I am having nightmares. Could the medication I’m taking be causing them? — Yes, nightmares can result from certain medications.

"Four criteria describe a nightmare: Sudden awakening from sleep with intense fear and anxiety; immediate recall of the frightening dream content; full alertness on awakening; and delayed return to sleep," Dr. Litt says.

One drug, in particular, that can result in nightmares and one that dermatologists might prescribe is ciprofloxacin (Cipro, Bayer). Other commonly prescribed medications are those used to treat high cholesterol, including atorvastatin (Lipitor, Pfizer) and simvastatin (Zocor, Merck).

Why is my lupus is spreading? — There are many possible reasons why lupus erythematosus (LE) might spread. Among the possible drugs to blame: sulfa drugs, such as sulfamethoxazole, trimethoprim (Bactrim, AR Scientific), dapsone, demeclocycline (Declomycin, Stiefel) and terbinafine (Lamisil, Novartis).

For the past few months I have felt like ants are crawling all over me. What can this be? — This tactile hallucination, or formication, is a physical or psychological side effect of substance abuse, namely from cocaine, crystal meth, Ecstasy and other drugs.

Dermatologists should consider these drugs if patients complain of formication; however, some commonly prescribed medications can also cause the reaction, including methylphenidate (Ritalin, Novartis), bupropion (Zyban, GlaxoSmithKline) and eszopiclone (Lunesta, Sepracor).

My husband’s penis is bent. Can that be serious? — Peyronie’s disease is usually more painful than serious, according to Dr. Litt.

"About 4 percent of men get it. Bill Clinton had it. And drugs can trigger it, including one that we frequently use: methotrexate,” he says.

For dermatologists, becoming aware of some of these rare and unique side effects of medications helps them to at least consider medications when patients complain of these reactions, Dr. Litt says. DT