The only side effect most of these products have is odor. Some of them were reviewed as being neutral to actually smelling good, while others were reported to have quite a strong smell you might not like. A lot of this has to do with the nature of the ingredients in pain relieving treatments. Mentholated ingredients give natural relief, but they do tend to have a strong odor that accompanies them.
Pycnogenol, like white willow bark, is a nutraceutical material that has been used since ancient times. Pycnogenol is derived from the bark of the maritime pine tree (Pinus maritima) and has been used for more than 2000 years. It has been considered helpful for wound healing, treating scurvy, healing of ulcers, and reducing vascular inflammation. It contains a potent blend of active polyphenols, which includes catechin, taxifolin, procyanidins, and phenolic acids. It is one of the most potent antioxidant compounds currently known.[17,118]
Traditional wisdom says that NSAID pain relievers only damage your gut lining if you take them every day for a long time, but recent research disagrees. High-level athletes with stress-related intestinal damage tried taking ibuprofen to improve muscle soreness and recovery. Ibuprofen ended up damaging their gut lining even further after just a couple weeks; it increased inflammation and made their original pain issues worse.[3] In fact, a single dose of aspirin can significantly increase your intestinal permeability.[4]