How do I reduce swelling from an insect bite if it's been days?

My 8 year son usually has reactions to insect bites such as itching and swelling which is usual , but also tends to swell up more than most people so I give him benadryl when he gets a bite. Two nights ago , he got bitten at least four times on one foot and his whole foot has been very red and swollen ever since. He has had three doses of benadryl and anti itch cream twice a day since then and his foot is still very red and swollen. I need other sugfestions since this is the first time it has lasted this long.

Here are few remedies:
Try rubbing the affected area with the inside of a banana skin. This reduces the swelling and irritation.
Take 2-3 teaspoons of cilantro juice as soon as possible and apply the pulp locally on the affected area. To make juice, blend a handful of cilantro leaves with 1/3 cup water and strain it.