A saliva allergy is a medical condition involving a negative immune system reaction, normally of the skin, that occurs when a person comes in contact with saliva. The problem is most commonly associated with pets and animals, although some people have asserted cases of reactions to human saliva, as well.
Doctors and veterinarians believe that a saliva allergy falls into one of two types. The first type happens when a person's immune system responds to the one or more of the proteins directly within the saliva. A person also may experience a reaction if the saliva contains something else to which the individual is allergic — most cases of human saliva allergy are thought to fall into this category, although much more research is necessary. For instance, if a person eats some peanuts, some peanut residue might still be in the mouth and saliva immediately following consumption and may cause a reaction in someone with a peanut allergy. In this case, the saliva is not truly the problem.
Sometimes a saliva allergy is difficult to pinpoint. For example, if a dog rolls around in the grass and then licks his fur, then allergens in the grass can transfer into the dog's saliva. If the dog licks his owner who is allergic to the specific allergens in the grass, it can appear that the owner is reacting to the saliva when he really is reacting to separate substances. Similarly, if the proteins in a dog's saliva truly are problematic and he licks his fur, the dog's owner might assume that it is the dander in the dog's coat that is the issue. Broadly, anything an animal licks can appear as the source of the reaction.
When a saliva allergy is present, sometimes the only way to prevent a reaction is to avoid the saliva. This is fairly easy to do with a pet — people can find the pet a new home, although this can be emotionally difficult. If the reaction occurs with human saliva, however, the allergy is more of a problem, necessitating at the very least a thorough examination of what a person who causes the reaction is eating and drinking.
Most allergies have a genetic link. This makes it unlikely that a person can get rid of a saliva allergy completely. The ability of the body's immune system to handle the allergen, however, is flexible based on overall health. To make things more complicated, genes can be turned "on" or "off" at certain points, meaning that not everything in the genetic code is always showing up. This explains why a saliva allergy, along with other allergies, may appear or disappear over time.