last week i got 5 bites on my legs, 2 of which were significantly bigger, redder and more swollen. they died down but now this week i have another bite whioch is very swollen itchy hot and red, i havent been outdoors, ive been working every day so no idea where its arisen from. its really distressing me getting thes bites so frequently. what can i do for th ecurrent bite and future prevention? is there any kind of injection against insect venom, or for bad reactions. help please