It might cause/contribute to swelling. My new mare had a swollen teat (just one). No heat, no pain, no fever, no discharge(she was seen by a vet). I removed flaxseed and the small amount of alfalfa she was getting from her diet. Both contain phytoestrogens. Clover apparently does as well. Interestingly enough, flax oil (processed) does NOT contain them, it’s in the seed hull apparently. Her swelling decreased in about a week. Her heats also bothered her less. I do agree with previous posts that allergies could also be contributing since she gets hives. Since the vet has already looked her over and treated her, there’s no harm in trying to eliminate other possibilities. Good luck.