How can I get a bruise from an insect bite?

Dear Ask The Doctor: I'm 16 years old. I attended a birthday party that was held in a park on July 9th. I noticed I got bitten by something below the side of my knee, but I just figured it was a mosquito bite or fly bite since everyone was getting bitten. Strangely though, it didn't itch. I didn't pay much mind to it... a few hours later I went home to take a nap, and when I woke up I had a huge bruise! The upper part of the bruise had a round skin colored circle, and around it was bluish black with weird purple dots scattered. I went to my doctor 4 or 5 days later and she claimed it was nothing. I STILL have this bruise, except now I can't tell if its getting better or worse. The purple dots have turned into purple streaks... I've researched online and I'm scared it could be something serious. I just want to know what it is, what could've bitten me, and if it could be dangerous... Thank you!

I honestly do not know what bug could have bitten you since there are various kinds of bugs out there and the geographic distribution is a factor too. The doctor who saw you should know the common bugs in your area and since he said it is nothing serious, I am confident he/she ruled out the bug bites that causes serious complications. It is possible that the bug bite has severed a superficial blood vessel, the ones just right under your skin that is why there is a bruise now. If an insect bite should cause worry, symptoms will be very apparent in a matter of days and in unfortunate cases, hours.  Symptoms can vary: difficulty of breathing, severe swelling and pain on the area, discharges (pus) on the area, etc. If you have not had these then there’s really no need to worry. Bruises also evolve in color over time. On the first day, it is usually red. On the 2^nd to 6^th day, it can turn bluish or purple then after a week it usually turns greenish. After that it may turn into a yellowish brown then after 2-3 weeks, it should go back to normal looking skin. These are only rough estimates and some individuals may heal longer and may take more days for bruises to resolve. Your bruise looks like a typical one and it is just starting to resolve. If the bruise still looks bad after 3 weeks, then it will be high time to see your doctor again. For now, just observe it as it will be likely to resolve on its own. I do hope I have appeased your concerns and take care always.