Some cells may even be destroyed by the irritant. When the irritant is removed, generally the symptoms disappear readily, the cells are repaired or replaced. If the irritant has destroyed a number of cells, scarring may result. There is a whole class of remedies chosen for their irritant effects called counterirritants. These may be rubefacient, producing increased local circulation, which in turn provides soothing heat and more nutrients for the cells.
Counterirritants also provoke a release of endorphins which reduce pain.
They are often included in liniments and other mixtures for sore, stressed muscles. There are counterirritants which produce more serious effects, the vesicants which cause blisters and the escharotics which sear and kill the outer layer of tissue producing a scar which prevents infection. This latter category is useful in serious wounds which happen in situations without other available medical care, but not of much use for us. It is important to remember that while an appropriate level of counterirritant in a mixture may produce desirable effects, a larger amount will cause damage to the skin. The cellular events that follow exposure and establish a capacity for responses of hypersensitivity are termed sensitization.