DEAR DR. DONOHUE: In the 1960s, my husband went camping with my son and a bunch of other Boy Scouts. Most of them returned in agony from poison ivy. I always felt that calamine lotion was messy and not too effective. My pharmacist suggest Ivy-Dry. It is marvelous. Other mothers tried it on their sons, and they were so appreciative they said they could have kissed my feet for suggesting it. Please stop touting calamine lotion and tell people about Ivy-Dry for poison ivy. – J.O.

DEAR DR. DONOHUE: How do you identify poison ivy? We have just moved to a place in the country, and I don’t want my kids to catch it. – R.B.

ANSWER: I am told that this year there is a bumper crop of poison ivy, so a few words about it are warranted.

It’s the sap of poison ivy that’s the villain. It’s a skin irritant, and the rash it causes is most unpleasant. It consists of small and large blisters that itch or burn. Fluid from the blisters does not spread the rash; only the plant’s sap does. However, sap can get on clothes, pets’ fur and other such things, and it can be transferred to human skin. (Pets do not come down with poison ivy rash.)

If you contact poison ivy sap, you have only a margin of 5 to 15 minutes to wash it off the skin before it gives rise to the rash that pops out anywhere from four hours to four days after exposure. Cold or cool compresses ease the distress of the rash. I haven’t tried Ivy-Dry, but my readers and I trust you and are signing up to kiss your feet – if it works. Antihistamines lessen the rash’s itching. So does baking soda paste and Aveeno baths (colloidal oatmeal).

Identifying poison ivy is difficult. The saying “Leaves of three, let them be” is helpful, but you need a picture to recognize it. You can find one in an encyclopedia, or you’ll find books on the subject in just about any library.

DEAR DR. DONOHUE: Please help. I have become terribly afraid of airplanes ever since the episode of the young man with the dangerous form of tuberculosis hit the news. It sounds to me like airplanes are health hazards. Are they? – B.L.

ANSWER: Airplanes are not places of great danger for the transmission of infectious diseases. In fact, similar enclosed structures on the ground are a far greater threat to the spread of infections. In a plane, 20 to 30 air exchanges are made every hour. In the carefully controlled environment of a hospital isolation room only 12 such exchanges are made hourly. The airplane’s air is passed through filters that remove close to 100 percent of all bacteria, viruses and fungi, including the TB germ. Air exchange occurs for every three rows on a plane. Only the people directly in back, alongside and in front of you breathe the same air as you, and that air is filtered. You don’t get such protection in a church, a movie theater, a restaurant or a school.

The man with what was then thought to be extensively drug-resistant TB is a special case. That germ, untouchable by so many TB drugs, represented a unique and dangerous situation, and that’s why such a fuss was made about it. If only one person were to be infected with that germ, that person could, in turn, spread this very unusual TB bacterium to others, and the threat of further transmission made everyone nervous.

You really do not have to fear air travel, but people with serious infectious diseases should stay off airplanes.

DEAR DR. DONOHUE: I need information about carotid arteries. One of mine is 100 percent blocked. I am told nothing can be done about it. Is that true? – M.R.

ANSWER: There’s a carotid artery on each side of the neck. These are the arteries that bring blood to the brain. If one artery is 100 percent blocked and a person has no symptoms, that person’s brain is being supplied with blood by other arteries. It does no good and is not necessary to operate on such an artery.

Blocked carotid arteries often lead to strokes. The booklet on that topic discusses these problems in depth. To order a copy, readers can write to: Dr. Donohue – No. 902, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com