And what triggered the allergic reaction if not the shrimp that you ate? If I have allergy to peanuts and eat in a restaurant and the cook slips some peanut in a food that is tagged "nuts free" and I die, can the family of the diseased press charges to the restaurant?

The answer is yes. A restaurant can be liable for food allergies. Whether a restaurant has legal liability or harm caused by a food allergy depends on whether the restaurant was negligent. Because it's the ingested food that caused it.