READ your skin. Aches, pains, itching, stiffness, etc. are all signs that something is going on inside. Acne, eczema and psoriasis could be inflammation or autoimmune issues. Reactions to certain foods, environmental toxins or stress are also common causes of skin ailments. Some of the common triggers include gluten, dairy, soy, eggs, and nuts. By doing an elimination diet, you can determine whether or not food is the cause.