If your horse is regularly hurting himself it could be interesting to ask an ophthalmic check by your vet. A lack or a decreased efficacy of vision could perturb the environment perception.
Concerning the mysterious swelling, check if there is a wound or some crusts. Some swellings are spectacular but the cause is small.. You can clean the localized wounds/crusts with soap (with neutral PH). If necessary, some antibacterial cream could be used too. For decreasing the swelling you can use: ice (protect the skin with a tissue between the ice and skin) and/or shower (with cold water) and give a dietary supplement : Or draining.
Of course a vet check is better for a more precise diagnosis.
Hope your horse will get better!
Join the fun and sign up to connect with our 200,000 members!