Spring is here, more or less. We got an early preview a while back that threw off the usual calendar, but the plants and trees have inched their way through colder temps since then. Early in the warm season, trees in particular are throwing pollen into the air. Other plants do as well, and depending on the month, different types of plans will release pollen throughout the growing season. Mid-summer tends to be a mix from grasses, with trees and weeds as well. Late summer and early fall are mainly weeds. All of this pollen is a bane for anyone with hayfever or asthma. (Believe me, I know this wholeheartedly — my hayfever gradually gets worse each year.) Itchy eyes, congestion, a sore throat — all of it’s part and parcel for breathing in the pollens carried around by the wind outside. Without the help of antihistamines, steroid nasal sprays, inhalers, and allergy shots, people would be utterly miserable. Pollen.com has a nice daily map for allergen counts.
Dogs and cats suffer from this type of allergy, too. There’s really no difference in how the immune system is behaving in response to exposure to all of this pollen. The unique part about allergies in dogs and cats is that they do a majority of the immune-related chemistry in their skin. Instead of the respiratory problems that people get, dogs and cats will get itchy, inflamed skin. When the allergy is to the things in the environment, it’s officially called “atopy.” On a quick side note, cats can get plain old asthma; and dogs can get allergic airway disease, too. I’m not going to cover those today, as they’re separate enough as topics to make up a whole other post.
When we are exposed to things that are not from our own body, the immune system has to identify these ‘foreign’ things and decide how to respond to them. This is the basic principle we discussed way, way back in the vaccine posts. (Immune Basics & Immune Responses) You’ll remember that we have to stimulate the immune system more than once in order for it to produce a good response from vaccination. The seasonal changes in pollen end up working much the same way. In this case, it’s an unfortunate turn of events. Young animals are exposed to all of these pollens during the first year of their life. This is a lot like the first vaccination. The immune system catalogs and learns the foreign material (pollens). Then, we go through winter with relatively low exposure. The next year, when the growing season begins, the immune system once again is exposed to these foreign materials. The problem is that the immune system often overreacts to this second exposure, and releases all kinds of pro-inflammatory chemicals that lead to redness and itching. The things that follow for allergy-suffering pets stem from that overreaction. Just as not all people suffer from allergies, not all dogs and cats do. We believe there is some genetic component, but the real reason for allergies developing isn’t understood.
Usually, I see a gradually increasing severity of signs and symptoms in dogs and cats. The first ‘bad’ year is just a little itching and licking here and there. Each year, the allergies get progressively worse, with more licking and itching, maybe a hot spot. Things get ugly from there: large hot spots, skin infections, hair loss, claw/toenail infections, and ear infections. It’s shocking sometimes to see how bad something as simple as a little pollen allergy can get.
Common clinical signs and history that we see include:
•Licking the feet or chewing the feet
•Redness of the feet, belly, and ears
•Licking/chewing/scratching at various areas on the skin
•Hotspots – areas of moist, red, gooey skin and partial hair loss; these are painful
•Ear infections (not as common with this type of allergy but sometimes seen)
When I first see a pet with mild signs, I will go over with the owner when the problems first started. Usually, owners will realize that there was a -little- itchiness in the prior summer. “This year it’s a lot worse” is something I commonly hear. We have to rule OUT a couple of other problems as we work on finding out about environmental allergies. Allergy to food ingredients and allergy to flea bites can also cause similar signs in pets. I’ll discuss those another time. Once we rule those out, or if the history suggests that the problem is very obviously seasonal, we have a preliminary diagnosis of Atopy — Environmental Allergies. One last quick note on the source of allergens: indoor allergens can cause atopy, too. Things like dust, dust mites, dander, etc. I’m focusing on the outdoor stuff because it’s seasonal.
Treatment for allergies is two-fold. First, I generally have to apply a set of band-aids in the form of treating the symptoms of the allergy. I have to help stop the itching, calm down the redness and inflammation, treat infections, and make sure that all external parasites have been ruled out or treated. These things don’t treat the underlying cause of the allergy, though. They help treat the symptoms. For some patients, this is “good enough” for that first couple of years. We give an antihistamine in almost all cases. Supplementing omega fatty acids helps. Sometimes, medicated shampoos or conditioners are useful. We have sprays for the skin, as well as antibiotics and – if things are really ugly – glucocorticoid steroids.
Ultimately, these bandaids aren’t enough. We have to treat the underlying cause of all of these secondary problems. Treating the allergy itself means we have to outsmart the immune system. The immune system produces a specific type of antibody that hooks up to a specific type of cell in the tissue. When allergens like pollen come in contact with these antibodies, the cells burst and release inflammatory chemicals. Repetitive low-level exposure to pollens makes more and more of these little grenade cells ready to respond at the next exposure. Left on its own, the immune system is hoist by its own petard.
What’s needed is a way to stop the pollen from ever contacting the explosive cells. This is done with allergy shots. Technically, this is called hyposensitization therapy. We allergy test dogs/cats with blood or by intradermal skin testing. Most people are familiar with the little tiny injections that the dermatologist gives you to see how big of a welt your skin makes. This allows us to put together a custom cocktail of allergens that are then made into a vaccine of sorts. The pets are treated with a series of injections of the things they’re allergic to, which creates a LOT of antibodies that circulate in the blood and tissue. What this does is create a massive standing army of antibodies that are ready to all pile onto pollen before it can contact those grenade cells and make them pop. We’ve used the immune system’s response to the allergy-causing pollen to create a defense against the pollen, which protects the pet from the inappropriate overreaction of the immune system. Neat, huh? Simply put, ‘allergy shot’ are a vaccine for allergies.
We also have a medication available for treating allergies that takes the opposite approach. Instead of using the immune system and provoking a bigger response, this drug suppresses the immune system and stops the bad chemistry from happening to begin with. This drug is a specially altered version of cyclosporine that makes the drug go to the skin more readily. The only drawbacks are that this drug is quite expensive, and many animals vomit while on it. Still, for owners that don’t feel comfortable with the allergy shots, it’s a good option. The few times I’ve used it, it’s been very helpful.
The take-home message for the day is: if it’s itchy, treat the -underlying cause- instead of just using bandaids. Thanks for reading!