A535, a nickname for RUB A535, which is manufactured by Church & Dwight in Canada, is first applied to the pain-ridden area with the hands. There are several kinds of A535, including a cream form and a patch form. The cream form is rubbed onto the affected area gently and massaged into the skin. The patch form is placed carefully over the affected area then pressed firmly into place until it has sufficiently stuck. Application of the medication is the first step in the process.
Immediately, the counter-irritants in the A535 begin their work. Counter-irritants produce a sensation that might be termed the "opposite" of the painful one your muscles are experiencing. In essence, they present an alternate, opposite sensation that the older, painful sensation must now compete with. This situation causes the pain to lessen as the body deals with both sensations--opposites--at once, and they cancel each other out.
A Confused Brain
The "battling sensations" typically produce a new sensation altogether, generally experienced as an "icy hot" feeling in the area where the A535 was applied. This new heat-cold combination distracts and confuses the brain, which is then forced to concentrate on this new sensation and pay less attention to the old, painful one. As a result, the original pain is considerably lessened (or disappears altogether).