Jeez! in the armpits!
Okay - most people in spas know this...
You are supposed to have a MSDS - Material Safety Data Sheet - on hand for any product that you sell.
This is supplied by the manufacturer.
If you made the product yourself you are 100% liable. This is why - unless you are a cosmetic chemist or something - you need to be very careful about selling products that you make - and they must include any possible warnings. You CAN be liable if you directed client to use the product inapropriately as already mentioned.
here is a link for the MSDS
http://www.hygenic-news.com/MSDS/BF_Gel.pdfAs I see it - there are no special precautions or danger of reactivity unless combined with acids and oxidizers.
So - the alcohol MAY have reacted with his deodorant.
As a general rule of thumb - any topical product can cause or result in an adverse reaction. Some people have sensitivities OR can become sensitized to a substance when it's applied to the skin that is in a reactive state - injury, trauma, other chemicals, recently exfoliated skin, waxing - even after a hot shower!
Don't be overly concerned - if you get too involved your client MAY try to hold you liable...thinking that is what you are all worried about. Any action should be on their part and taken up directly with the manufacturer. Oh - and see if there are any warnings right on the tube so you can become more familiar with any possible problems for the future.