What are the potential thundershirt side effects that I should be aware of before using it for my pet?

Some potential side effects of using a Thundershirt for your pet may include skin irritation or discomfort if the fit is too tight, potential overheating if used in hot weather, and the possibility of the Thundershirt not being effective for all pets. It's important to monitor your pet closely when using a Thundershirt and consult with a veterinarian if you have any concerns.