When my daughter first started riding at the age of four, she was very small. Although the horse she was grooming was known to be a quiet, senior horse, when she walked behind him (big mistake) to groom his tail he kicked her in the head.
THANKFULLY I had the presence of mind (being a horse person myself) to put her helmet on BEFORE she started grooming. When that quiet, senior horse kicked her square in the head, her eyes crossed a little and she cried. She said her head hurt but she still wanted to ride. Fearing a concussion, I laid her on some hay and removed her helmet. She had a small red mark where the interior padding made an impact but clearly the helmet DID IT'S JOB. There was no lump, no swelling, no BLOOD...
I asked to be given a different horse and allowed her to ride. She switched to her favorite lesson horse and was happy as a clam despite a headache. My daughter has continued to ride for 10 years winning many championships on the way but SHE NEVER EVER goes without her Troxel!