If you travel to tropical environments (especially to beach areas in those environments) you are likely to encounter various insect bites. The article below describes some of the likely suspects and goes over some useful treatment protocols.
Sand Fleas and Flies
I’ve had quite a bit of experience dealing with sand fly bites in the Caribbean, Egypt, and South America. Besides the advice provided in the linked article above, I have a few more suggestions.
If the hydrocortisone cream recommended in the article isn’t stopping the itch, you could also try a topical corticosteroid called triamcinolone. It is commonly sold in foreign pharmacies and is more potent than the OTC hydrocortisone you can buy here in the States. The triamcinolone shouldn’t be used on sensitive areas of the body (genitals, face, etc.) because it may cause irritation or skin thickening. I’m not a doctor and this isn’t medical advice, but I’ve had good luck with this product if OTC hydrocortisone fails.
If the rash persists for more than a couple days, visit a doctor. You may also check out the local pharmacy. In most countries in the developing world, pharmacies sell tubes of combination steroid/anti-fungal/antibiotic creams over the counter. That makes a precise diagnosis unnecessary if you can’t make it to the doctor. No matter what is causing the skin irritation, these multidrug creams take care of the problem.
If itching insect bites or rashes are driving you crazy and you have no medication, try hot water. Place the affected area under water (as hot as you can stand) for three to five minutes. The hot water might neutralize the toxins that cause the rash. The effect is only temporary, however. You may need to repeat the process every couple hours. Ammonia may also work to temporarily relieve the itching from some bites.
The author of the linked article wrote a book called Survival Medicine. Check it out if you are looking for more medical information. It is an excellent reference.
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