I use them in the hot weather months. I use stressdex the same as I give my horse. I just add about 1/2 teaspoon to their food every couple of days. My dogs work all year round equally hard & I feel that this just replaces some of what they loose. My dogs are also on a raw diet & due to that fact they get alot of fluid in their food but the stressdex just adds that little bit beyond the fluid alone that they need in the hot weather. I have not noticed any illeffects from doing this.