Gluten in non-edible items

Gum on postage stamps and envelopes

Extensive enquiries with the Post Office and the manufacturers of envelopes have shown that the gum used in these products is gluten-free and safe for people with coeliac disease.

Cosmetics (make-up, face creams etc)

Gluten poses a problem for people with coeliac disease if it is ingested i.e. taken in via the mouth.  It cannot be absorbed through the skin.
 
With regards to lipstick and lip balms, if any ingredients are derived from a gluten containing cereal, it is unlikely that you would swallow enough of the product in question to cause a response. If you are concerned then you should contact the manufacturers directly about specific products.

It is still possible to be sensitive to ingredients used in cosmetics, but this has nothing to do with coeliac disease specifically.