Every time my daughter goes to my ex for the weekend she is sick help

Could be this, could be nerves about the situation, could be ANYTHING. Have you been able to ask him/ talk about it?

Quoting gigules04:

There might be something over there that she's allergic too! My daughter did the same & she does it @ my mom's too! She has a dog & my daughter's allergic to the pet dander!

Try following up yr daughter while she' at his place,bse he too might not be knowing abt it.

Quoting emmy526:

does he or anyone else smoke around her?  Are there pets at his house?  Does she have on adequate clothing over there?  Is she wearing her coat outside?   How late does she stay up?  What does she eat?  Those are the things you should be asking about.   

I know this might sound weird but does he have a carbon monoxide detector those are sign of a leak and if you add lack of regular sleep and nutrition or even water you could see these signs.  Just something to check

What temperature does your ex keep the house?

Do they smoke in the house or around her in the car?? When ever my kids went to my neighbors house they would come back coughing and hacking like they had an awful case of whooping cough,I found out that both she ,her husband and two grown sons all would sit there in the livingroom and smoke like chimneys ,while the kids would be sitting there watching t.v. or trying to eat.I would check that out .

Mold?

I'd say the best thing to do is invesitage. Go with your daughter next time or talk to her/your ex in private (seperately)

Ask him to keep a food journal (every single thing she eats/drinks while in his care) so you can rule out food allergies - do it yourself for a few days before so you can show him.

I know how you feel. My 4 year old gets sick almost everytime she goes to her dads, he smokes around her, he feeds her crap and she also has come home with lice many times. It's been over a month since he's seen her now, his fault though, not just me keeping her from him. Hope you can figure it out!

 something enviormental... like something she is allergic to, something in the home like lead paint (older home) or mold (in the basement, foundation or walls)..

It could be something she is eating, or depending on her age it could be behavioral...