Any information provided by your ingredient suppliers on the potential unintentional presence of allergens should be passed on to your customers. So, you should pass on any ‘precautionary allergen information’ such as ‘may contain…’ or ‘not suitable for…’.
The FSA recommends that information on the unintended presence of allergens for PPDS foods is communicated on the packaging or label to ensure that the allergic consumer is aware of the risk. But you can also provide this ‘precautionary information’ in another form such as on a sign or orally by staff.
This type of information should only be provided if a real risk of allergen cross-contact has been identified following a thorough risk assessment that cannot be removed through risk management actions, for example segregation and cleaning.