It's down to the individual to tell you whether they can use the product or not. I've asked about this in the past because I have a nut allergy (not the serious anaphylaxis reaction that some people suffer from but its an allergic reaction none the less). People have told me that its not a problem because your customer isnt eating it, however I have noticed personally that I've got a bit breathless and blotchy on occasions. I know we dont eat the oil, but we do put it on our fingers, then eat our food, put our fingers in our mouth etc, so it's just sensible to check with your client for a nut allergy.
The nut allergy question is on my client consultation form, and if a client has a nut allergy then I have a small bottle of cuticle oil standing by that doesnt contain nut oils. I've only ever come across one client in the whole of my working life who was allergic so its not a massive issue, but still its an issue to be aware of and err on the side of caution :hug: