Q: About 30 years ago, I slammed my thumb in a heavy desk drawer, below the nail bed. It hurt like the dickens, and through the years the nail has become uglier and uglier - thickened, very wavy and dented, but now it is beginning to discolor.

I’m starting to wonder if this is due to a fungal infection. If so, would one of the remedies for toenails help my thumb?

A: Other readers have noted that an injury to finger- or toenails may lead to a subsequent fungal infection. The remedies that work for toenails should be helpful for fingernails.

They include soaking the affected nail in a variety of antifungal solutions, including dilute vinegar, cornmeal mush, Pau D’Arco tea or hydrogen peroxide. Applications of vitamin E oil, Vicks VapoRub or tea tree oil also have been reported to be effective.

For more details on these and other approaches, we are sending you our Guide to Hair and Nail Care. Anyone who would like a copy, please send $3 in check or money order with a long (No. 10), stamped (70 cents), self-addressed envelope to: Graedons’ People’s Pharmacy, No. H-31, P.O. Box 52027, Durham, NC 27717-2027. It also can be downloaded for $2 from our website: www.peoplespharmacy.com.

Q: I am on a website where information is exchanged between people with type 1 diabetes. Half the people say that insulin doesn’t need refrigeration after it is opened, and half say that it still needs refrigeration. After having diabetes for 42 years, I have never heard that keeping insulin at room temperature is OK. Is it? Doesn’t temperature affect how well the insulin works?

A: The American Diabetes Association recommends that a bottle of insulin can be stored at room temperature (59 to 86 degrees F) for up to one month after it is opened. Storing it in the refrigerator after opening does not make it last longer.

Unopened insulin can be stored at room temperature for one month or in the refrigerator (not in the freezer!) until it reaches its expiration date. Insulin must be protected from extremes of heat or cold, which means not leaving it in the glove box or trunk of a car during the summer.

Mail-order delivery can pose problems. One reader had a delivery of insulin sit outside for hours in the winter. The pharmacy told her it should be fine, but it did not control her blood sugar properly. If you get your insulin by mail order, check with the pharmacy to verify that it will not sit in a hot delivery truck or mailbox in warm weather.

Q: Can you use amber Listerine as a mosquito spray?

A: As far as we can tell, DEET remains one of the most effective mosquito repellents, but many readers prefer to avoid this chemical. They have tried many alternatives, including eating garlic or taking vitamin B-1. Some use applications of catnip oil, basil oil or oil of lemon eucalyptus (Off! Botanicals, Repel Lemon Eucalyptus, Fite Bite).

Listerine may be another option. One reader reported: “A couple of years ago, I read in The People’s Pharmacy about Listerine (original amber) as a mosquito repellant. I mix it half and half with water in a spray bottle.

“Spray your arms, legs, around your body or under a picnic table where they collect. You can use the house brand to cut expenses.”

No one approach works for everyone. Some people are especially attractive to mosquitoes, so you may need to experiment.

Joe and Teresa Graedon answer letters from readers submitted on their website www.PeoplesPharmacy.com. Their newest book is “Top Screwups Doctors Make and How to Avoid Them.”