Mucous membranes are the inner side of organic systems such as the nose, oral cavity, intestines and others and must always be able to exert an adequate immune response to eliminate pathogens. If some ingredient or chemical disturbs this pathway, the mucosa may not be able to defend itself against external agents and may become diseased.

Most of these ingredients and chemicals are reported, but sometimes individual intolerances appear.

So it is always a good idea to check the composition of creams, soaps, shampoos before use.