lower leg Rash

I am really worried about what this rash is, and was hoping some one could tell me.

The rashes are on both of my lower legs, there are a few above my knees but not many.  There are also  2 or three on my arms, but on my lower legs it looks like there are a million bug bites.  They extend down to my ankle but not really to my feet.  When I stand or walk sometimes I feel pressure on my legs and it sort of hurts.  Each one looks like a little red bug bite.  They aren't really itchy but they are itchy places once in a while (one time in a day).  I got all of the rashes over night.  Not sure if this is significant but I boxed two days before the rashes appeared and after I felt a lot of pressure on my lower legs.  Can someone please help me out or point me in the right direction?  
By the way not sure if you could use this information, but I'm and 18 year old male and this is also the first rash I've ever had.

[Vanessa Lacuesta]

Hi

Rash in the lower extremities may suggest several things: It may be infectious, vascular, allergic or autoimmune. In your case, we have to consider an infectious or allergic process first as you are young. You have mentioned that you have engaged in strenuous activity prior to the occurrence of the rash (is this correct?). In this case, then we may need to rule out possible triggers which could have caused the rash. These triggers may be allergens as in the case of protective gears attached to the lower extremities, lotions applied, any food intake or even pressure or trauma to the area.

Were any of these noted?

[james212]

Hi

Thanks for the reply.  I wasn't wearing any protective gear except for gloves, and I can't recall using any lotion or anything.  A few bumps that look like bug bites appeared on my arms too but not nearly as much as my legs.  And some of or a good amount of the rash on my legs are turning purplish or a darker shade of red.  I find that when I stand it tenses the side of my calves and my veins sort of stick out.  My veins tend to be more visible because I'm a little underweight for my height and age, but thought it might be a clue to as to what this is.  As to the strenuous activity, I did feel a lot of pressure in my legs and a little pain and its the same feeling as when I'm standing for a long time and feel the pressure.  Do you think this will go away anytime soon?  I showed my doctor and he gave me antibiotics, but at that time (2 days ago) I didn't feel pressure on my legs when standing, there weren't any bumps on my arms, and they turn purplish or dark red.  Would you suggest I go see my doctor on Monday?

By the way, thank you for helping