DEAR DR. ROACH: Two years ago, I spent a month in Havana, Cuba, to study Spanish. We were staying in a good hotel. Without warning, one morning they started the pest control, spraying the rooms with DDT. The substance was confirmed by our group leader. Our clothing and belongings stayed in the rooms, and we were told to stay out for three to four hours. The fumes were thick and heavy. Afterward no cleaning was done, no bedding was changed, and we had to sleep with smelly sheets breathing the fumes.

When I got back home, I started having a feeling like something was “crawling” on the back of my head. I thought I had lice, and I used two over-the-counter treatments (permethrin) to get rid of them. After that I went to a lice clinic to make sure I didn’t have them. The clinic confirmed I definitely do not have lice. The crawling sensation continues, and it has moved from the back of my head to the left temple. It’s always in one spot. It started on the back, the next time, it moved to the left, and now it’s on the left temple. It can go away for a few days. It started right after the Cuba incident, and I have never experienced anything like this before.

Is it possible that this was caused by the DDT or the lice treatment that I used? What should I do to get rid of it? — R.M.

ANSWER: DDT was banned in Cuba in 1970, and although some reporters suspect the continued use of DDT despite that, there is no convincing evidence that this is the case. The spray that pest control used almost certainly was permethrin, the same substance you used to treat lice (which I don’t think you ever had). Permethrin is well-known to cause nerve symptoms, especially itching and a pins-and-needles sensation. I wonder whether, with two lice treatments on top of the exposure in the hotel, you developed toxicity from permethrin.

However, I could not find any evidence of long-term damage from permethrin. There are no case reports of people having symptoms so long after exposure. So, while it is possible, that seems unlikely.

The fact that it moves around a bit on the scalp also suggests no permanent nerve damage, as does the fact that it can go away for a few days.

I don’t know what’s causing your symptoms, but many times, worry related to illness, infection or infestation can lead to very real symptoms. It is possible that you are so worried about having been damaged by the exposure that some part of the physical symptoms is due to being so (understandably) nervous about it. I certainly recommend that you visit a dermatologist to be sure there is not some skin condition you can’t see that is unrelated to the exposure.

DR. ROACH WRITES: Some users were confused by a recent column on the use of the HPV vaccine to treat stubborn nongenital warts. I noted that the HPV vaccine, Gardasil, initially was approved for use in females (age 11 or 12 is recommended, but may be started at age 9 and up to age 26) to prevent cervical cancer. It subsequently was expanded to include males at the same beginning age and up to age 21.

I agree with the recommendations, and vaccinated my own daughter and sons after carefully reviewing the evidence of benefits and possible harms.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.