What is mode of exposure in allergic reaction to new carpet?

Question

In reading about allergies associated with a new carpet installation, such as a skin rash, it's not clear exactly what the mode of exposure is. Is it from breathing in the chemicals that are outgassing, contact of the skin with the air laden with such chemicals, or physical contact with the carpet? Or can it be any of the above?

I've been asked to provide information on what I have read on this subject. So for instance slide 3 of the WebMD article is typical of what I've read (Is your house making you sick?) and simply says "The chemicals used to make and install some carpeting could be bad for you, too" but does not address the questions I raise above in regard to skin rash. A Mayo Clinic article (Latex Allergy) does states that it could occur by direct contact or inhalation, but I haven't found something like that for carpet chemicals as they relate to skin rash.

Answer 1

TL;DR: All of the above.

An allergic reaction can be caused by any form of contact with the allergen. The contact can be physical skin contact, inhalation, ingestion, having it injected -- any contact at all. And although the gasses emitted by manufactured products don't usually involve proteins and therefore can't cause "true" type 1 hypersensitivity reactions, they can combine with other proteins to form substances that can act as allergens. Metal and drug allergies are good examples, so carpet chemicals could do the same.

If you've ever seen the contents of a vacuum bag after vacuuming a carpet, you know that carpet fibers come loose and float around, and they're small enough to be inhaled or swallowed without notice. So there's the potential mechanism for skin contact, inhalation, and ingestion all in one.

The same is true with outgassing. If the carpet is outgassing, those gasses will be inhaled and can combine with proteins in the environment or your own body to form haptens. They can also be irritating in and of themselves and so can mimic a "true" allergic reaction. That would be a type IV hypersensitivity reaction caused by:

Contact hypersensitivity dermatitis occurs when haptens, which are considered as exogenous antigens, penetrate the skin with proximity to epidermal and dermal cells, resulting in an inflammatory reaction.

So the answer is that being in close proximity to a carpet containing anything you have a sensitivity to can potentially cause an allergic reaction through multiple modes of contact.