Large Blisters on Legs

Please help!  For a few years now, always around the end of the school year/summer, I get large blisters on my legs.  Some years it has been one leg, sometimes it has been both.  Please excuse the fact that I dont know the technical terms for things, but I'll try and describe it the best way I can.  The blisters are almost always perfectly round, most of them about half an inch in diameter.  They are tall, and the best way I can describe them are ''bubbles''.  The blisters tend to stay below the knee, but are very itchy and uncomfortable.
One year, i noticed a large bug-bite type thing on my knee. It wasnt the summer yet, so i was still in school and knelt down on it quite often to get to my locker.  The spot seemed to get larger and moist-er and redder.  Then it bubbled up all over my knee and was very wet.  Then the usual blisters popped up, on both legs this time though.  I would appreciate insight.  The blisters eventually stop forming, heal, and go away after a few weeks.  But they are very inconvenient when I want to enjoy summer.

[ovaltinecat]

Also, let me add that I am fourteen years old, female, and sometimes have bad reactions to mosquito bites (never boils, though).  It used to happen when I was at the beach, where there were biting flies in the sand.  I thought that was the cause, but I've gotten the symptoms without going ot the beach before.  I'm getting nervous about it, because its nearing the end of the school year and today I noticed a patch of red bumpy skin on my knee.  I fear its going to happen again this year (I've had a two-year repreive from symptoms since it last happened)

[Bhupinder Kaur, MD]

Hello,
I cannot confirm anything without examination but these leg blisters can be due to friction rub or chaffing with clothes,cellulitis or erythema multiforme.

Erythema multiforme is a type of allergic reaction that occurs in response to medications, infections, or illness.Most likely it sounds like rash due to friction rub,but it is important to rule out the other conditions.Pls consult a dermatologist for that.

Hope it helps. Take care and pls do keep me posted on how you are doing or in case you have additional queries. Kind regards.