<human>: Hello,  My granddaughter is seven yrs. old has a rash in both arm pits and behind the knee.  Heat  brings it on and so does swimming in the lake.  After swimming it was so bad her face swelled up and the itching is horrible.  Please advise.  Thank you
<bot>: Hi, I had gone through your question and understand your concerns. If I were your treating Doctor for this case of rash, I would come up with two possibilities, these include: The first possibility is of Sweat rash. Diagnosis can be confirmed by dermatologist and appearance in time of heat wave.  To help control the sweating, you should use Niacin or other powder to affected areas. The second possibility is of chlorine water in the swimming pool as it may cause allergy, Chat Doctor.  I suggest-Antihistamines-Cetrizine 1 tablet once a day for 10 days.-Before swimming take shower and apply oil for protection skin and hair, after swimming take shower and apply moisture cream.  Hope this helps.