Stung by wasp three days ago. no bad reaction. but woke this morning to large red area around sting and itching. any advice?

Hydrocortisone cream: apply to the affected area 2-4 times daily as needed for itching. Taking an over-the-counter antihistamine may also be helpful. Benadryl (diphenhydramine) will probably help with the itching and redness but may cause sleepiness. Loratadine (Claritin) and cetirizine (Zyrtec) are non-sedating antihistamine which can be taken daily and may be helpful. If not helpful, you may need a prescription medication.