### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
Whenever I eat crab I vomit and have diarrhea within an hour or two of ingesting.  Ive had four incidents in the last two years.  It took a while for me to even think it may be crab as Im lactose intolerant and kept wondering what dairy did I have to cause the reaction.Ive seen an allergist and both skin and blood tests have come back negative for crab and other shellfish.  Even though the tests have come back negative should I be concerned about anaphallxis and carry an EpiPen?  Either way Im not eating crab again.

### output:

Hello. Thank you for asking at Chat Doctor. I went through your history and would like to make following suggestions to you:1. If your allergist has made diagnosis of anaphylaxis, it is highly desirable to carry EpiPen as its prompt use can be life-saving should you have any episode of anaphylaxis. There is no specific test to diagnose anaphylaxis retrograde, so diagnosis CN be assumed only after knowing the details of episodes.2. I usually think of diagnosis when more than one system are involved - any two of gastrointestinal, cardiovascular, respiratory and skin. So, if you have only vomiting and diarrhea (gastrointestinal) associated with crab, and no other symptoms like fainting, hypotension, collapse, palpitation, cough, respiratory difficulty, wheezing, swellings, itching, hives, etc., I would not first think of anaphylaxis. As your allergy tests are also negative, I would first think of non-allergic intolerance or something like food poisoning. However, if you have any of the above-mentioned symptoms, anaphylaxis would be my first consideration, in that case, EpiPen will be a need for you. Hope above information will help you. Thank you & Regards.