There have certainly been many exciting developments in recent years in the fight against flea and tick infestation, as well as heartworm prevention, in our companion animals. Newer oral and topical products are constantly being developed in order to hopefully stay ahead of emerging resistance to these external parasitic pests to our dogs and cats. Fortunately most of these products have been developed with increasing safety; however, there are still occasional animals that will suffer allergic reactions to any potential external or internal pesticides.
For example, with topical products, the most common reaction is irritation and hair loss at the site of application. This usually occurs within minutes to hours of application and can cause considerable distress to the animal. Treatment would include bathing off the topical residue and applying topical antibiotic/cortisone creams. If reaction is prolonged or excessive, then a veterinary consultation is always recommended.
The most common side effects with the internal pesticide products include digestive upset such as vomiting, diarrhea or transient loss of appetite. I find that this issue seems to be most common in the combination products, or when two separate products and/or vaccinations, etc are given on the same day. It is always best to try and separate out immune challenges to our companion animals, separating the use of different products by at least 7 days, as well as not vaccinating pets on the same day as application or administration of the product.
Sometimes giving the oral products with food can help cut down on the risk of digestive tract reaction. I will also sometimes have clients administer over-the-counter Pepcid before administering the oral product, which may protect against stomach upset. If digestive tract reaction is severe, then an alternative oral, or preferably a topical product for flea/tick or heartworm prevention is recommended.
Probably the most disturbing rare reaction to either topical or oral pesticide use in veterinary medicine are neurological reactions, which may include restlessness, panting, hypersensitivity along the spine, twitching and even occasional seizures. Fortunately these neuro reactions are probably seen the least of the potential reactions to these products. In the latter case, a veterinary exam and consultation would always be recommended.
For those pets who are exquisitely sensitive to both topical or oral pesticide products, there are natural alternatives, including herbal black walnut, quassia bark, diatomaceous earth, as well as various essential oil products. These latter products, however, should always be used under the advice and care of a holistic-oriented veterinarian, as the traditional conventional veterinary community still does not accept most of these as trustworthy and reliable products for controlling and preventing flea, tick and heartworm infestation in pets.