Hi, Horsefly bites can be quite painful and can cause an allergic reaction in some people. Based on the symptoms you described, it sounds like you are experiencing a localized allergic reaction to the horsefly bites. The red circles around the bites, swelling, and pain are all common symptoms of an allergic reaction. Taking a 25mg Benadryl (diphenhydramine) was a good first step in treating the reaction. The usual adult dose for Benadryl is 25-50mg every 4-6 hours as needed. However, you should not exceed 50mg in a 24-hour period unless directed by a doctor. In addition to taking Benadryl, you can continue to apply topical creams like the Benadryl and cortisone that you used. You may also want to apply a cold compress or take an over-the-counter pain reliever like ibuprofen or acetaminophen to help with the pain and swelling. In terms of watching for symptoms, you should monitor the affected areas for signs of infection, such as increased redness, warmth, or pus. If you develop a fever or other systemic symptoms, you should seek medical attention. If you have a history of severe allergic reactions or if your symptoms worsen, it s always best to seek medical attention immediately. An allergist may recommend that you carry an epinephrine auto-injector with you in case of future severe reactions. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Diwashish Biswas, Internal Medicine Specialist