Mastocytosis is a somewhat rare condition. However, the term can be used more commonly for a group of skin reactions. I encourage you to talk to your doctor
further. A dermatologist
may also be of help to further address your wife's skin condition.
Mastocytosis is a group of disorders that all have in common excessive mast cell activation. Mast cells, are part of the body's allergic response system. They release many chemicals (most notable histamine) that cause an allergic type reaction. There is two large categories of this condition--cutaneous (which is limited to the skin) and systemic (in which the organs inside the body can also be affected). A classic sign of mastocytosis is Darier's sign--which is when a rash and itching results from somebody rubbing the skin. This disorder is caused by mutations in the immune system.
However, the term mastocytosis, is sometimes used when people have a skin reaction that looks allergic. In this case, the mast cell activation is not abnormally excessive (as in the case of the primary disease) but actually an appropriate response to some allergen (like detergent).
In the later, symptoms control and allergen avoidance is appropriate. In the former, a more complete workup is often warranted to rule out systemic problems. I encourage you to speak to your doctor and or a dermatologist to better understand what the diagnosis is.