I have more than 20 mosquito bites on my leg and it's bruising?

Bruising: small bites cause blood to come to the surface of the skin: multiple mosquito bites can look like bruising, but really related to superficial blood drawn to the surface during the bites. I suggest OTC antihistamines and 1% hydrocortisone cream.

Topical treatment: Use cold compresses and caladryl. Try and stay indoors and away from mosquitos for a few days while they heal.