Hello - I am sorry she is so sick on arriving here. Here are a few thoughts to consider: 1. If the vomiting came on rather abruptly and rather violently, and is accompanied by feeling feverish, chills, light headed/dizziness, it may be food poisoning from something she ate which could be the clams or something else, including air plane food if she had it. 2. If the vomiting has not been accompanied by abrupt illness as described above, it may be a viral gastroenteritis she could have picked up before or while traveling. This can last for a day or more. 3. If she has a history of allergies to shell fish, this could also cause vomiting, but usually other allergy related symptoms too, such as rash or swelling of the tongue/throat. So an allergy causing this vomiting is lower on my list. If she is still vomiting 5 hrs later, and not able to keep anything down, then she may be getting dehydrated and possibly an electrolyte imbalance (vomiting causes loss of potassium in particular). If she isn t able to match the fluid and electrolyte losses with rehydrating fluids like coconut water (NOT coconut milk) and water, and is having persistent vomiting, it s time to go in to an ER or urgent care. It would need be a place where she can have her electrolytes drawn and get the results back rapidly (i.e. have a lab associated with it), and get an IV for rehydration and correction of electrolytes and possibly receive some glucose in the IV solution - if it isn t run in too fast - usually the first bag of IV fluid to correct the dehydration, using normal saline or lactated ringer solution, run in fast, then the next bag can have glucose). They can also give her an antiemetic IV or IM. Sometimes just giving the GI tract a rest with an IV and correcting the losses is enough to quiet it down. I hope this helps and she is feeling better soon. I don t know at what time you wrote in this question as we only see the time on the for-pay site questions, so I hope if this is coming later rather than sooner, that she has gone in for help.