If someone is allergic to shrimp, are they also guaranteed to be allergic to lobster and crab as well? My step-daughter brought out in hives after eating shrimp one time and refuses to eat lobster or crab as well now, although she has never tried them. Is there a safe way to find out? Does that seem correct?

She can ask her doctor, and she probably already has, since she seems to be following sound medical advice. If you're allergic to shellfish, you can't eat shellfish. It's very tragic but since she has never eaten lobster or crab she'll never know what she's missing.

Some people may be able to eat shellfish if they are allergic to shrimp, but most CANNOT.

The only "safe" way to find out is to speak to her physician and then undergo allergy testing.

she should go get real medical assistance, not base her live on hearsay from people who do not know what they are talking about. an allergist can perform "scratch" tests and pretty much determine many major allergies. many things do not have test seriums. my mother had extreme reactions to strawberry, corn, crab, tomato. no problems with shrimp and lobster. she got severe migraines.

the tests are simple, and have been around since at least the end of ww2. i had my first scratch tests in 1947 when it was determined i was allergic to grass molds. we lived in illinois, which is a major wheat producer. i could not breathe through my nose till i moved to boston. in 1947, i think they had about 20 items for which to test. the last time i was tested in about 2005, they had hundreds of test items. there were at that time tests for only about 5 or 6 different tree pollens. i am allergic to one of them, but not one of those for which tests are available.

From the Mayo Clinic

A shellfish allergy causes an allergic reaction when you eat shellfish. Sometimes, a shellfish allergy is only to certain kinds of shellfish, or you may have an allergy to all shellfish. Shellfish include marine animals with shells, such as shrimp, crab, and lobster, as well as octopus and squid.

I've known quite a few people with shellfish allergies, none of them would touch any shellfish, they did not feel it was limited to just one.

The safe way to find out is to get tested by an allergiest or whatever. There's no way to tell by sneaking crap or lobster into her dinner one day to see if she gets a free ride ambulance ride or not.

I'm allergic to all shellfish. I became ill overseas this spring when the chef accidentally added shrimp to my meal, after I informed the waitress/kitchen that I wanted the shrimp excluded. Bottom line: don't take any chances.

A medical doctor or naturopath can give you a clear answer. You might try a clinic or college of natural medicine in your area, too. We have such a college in Seattle that tests for allergies and they charge on a sliding fee scale.

Really? Then one should probably consult someone qualified. Perhaps a physician*, not a quack.

Anyone can provide clear answers; I'd prefer correct answers. Some MDs (e.g. allergists) may be qualified to reliably provide correct answers.

I would hesitate to risk my health to a practitioner of a practice that uses a "treatment" technique (homeopathy) that can only work if our current understanding of chemistry and physics utterly flawed.

*: A naturopath is not a physician in CA (OP's location).

a physician (general practitioner) is not qualified to adjudge one's allergies. there are trained allergy specialists. the one i went to(one tends to outgrow allergies) had thousands of test samples available. any competent MD would only tell an allergy suffer to go to a trained allergist. they may recommend one. in the greater dc area, there are about 50 practicing specialists.

I'm severely allergic to a few things, some of which are not available as 'scratch tests' (because they are unusual allergies) but the reactions are undoubtedly allergic reactions (per more than one MD)

I also tested positive to several substances on the scratch test that I am convinced I am not allergic to, because of extensive exposure. It told me I was severely allergic to dogs for example - and yet I've lived very happily with dogs my entire life with not so much as a rash or sniffle (doctor was astounded, said she would expect heavy wheezing if there were dogs near). I was also allergic to shellfish - and whilst I haven't eaten shellfish since I was around 5 years old, as far as my mother remembers (and I believe her memory and my own) I never had a reaction.

So I do wonder about the accuracy, certainly in terms of false positives.

Like others have said, the answer is a definite maybe.

The odds are pretty good and it's not worth taking the risk if she's not sure.

Her GP can refer her to a specialist who can do scratch tests, etc to most likely determine the extent of her allergies.

I'd hate to be condemned to a life time without shrimp or shell fish. There's always the possibility that her hives outbreak had nothing to do with the shrimp. A referral to an allergist (sometimes covered by health insurance, if the MD will take it) can quickly establish the nature and extent of most food allergies.

As a caveat, I've a brother in law who is an allergist, and I think he puts his trust in God, but all others pay cash and file their own insurance claims.

Shrimps, crabs and lobster are all in phylum Arthropoda while squid and octopus are in phylum Mollusca. So, you will not necessarily be allergic to them all just because they come from the sea.