If I sign a waiver/indemnity but then have an allergic reaction, can I still report the food service business for investigation (if I have clearly communicated my food allergy)?

Although the terms of each waiver/indemnity will differ, a term of a waiver/indemnity that tries to prevent a person from reporting a food service business to the relevant authorities would likely be invalid on the basis that it would not be in the public interest to prevent food standards regulators from being alerted to possible food safety issues.