Q: My friend’s 3-year-old filly plays with her tongue so much that she foams at the mouth (without a bit). She also plays with the rails in her stalls at feeding time such that she has foam all over. She is not cribbing or sucking air. What could be the problem?

—via e-mail

A: Between the ages of 2 1/2 and 3 1/2 years, most horses will shed 16 baby teeth and erupt 16-20 permanent teeth. If some of these baby teeth remain in place too long, they can become loose, sharp, or otherwise painful to the horse. Likewise, baby teeth and brand new permanent teeth are relatively soft and wear their edges into sharp points quite quickly. One of the most common physiologic reactions to oral pain is hypersalivation (overproduction of saliva), which in turn can lead to mouthiness and licking, especially at feeding time when saliva production increases anyway.

I would recommend that a veterinarian experienced in equine dentistry examine the horse and make sure that her mouth is balanced, comfortable, and has no retained baby teeth. This is a very good age for any horse to have a comprehensive dental examination. Other problems that could cause the signs you describe might include foreign material lodged in the mouth, chemical irritation, or a primary salivary problem (which is rare). It is also possible that the root of the problem is behavioral, with excessive licking leading to hypersalivation. However, a thorough examination of the horse’s oral cavity will most likely provide the answer to the problem