Contrived allergies

I have two kids, one of whom is a 6 year old boy.  His mom, my ex-wife, is convinced that he has numerous allergies - none of which he has tested positive for.  These include allergies to ALL food dyes, latex and perfumes.  She insists that I wash his clothes in a dye and perfume free detergent and that he avoid all food dyes and anything latex, like balloons.  I have spoken with his various allergy doctors and he is NOT allergic to latex or perfumes.  Likewise, he is not allergic to all food dyes.  He MAY have an allergy to one or two specific dyes, but certainly not to all.  Children being as they are, he had food or drink with dyes and has had NO adverse reaction whatsoever.  Even if he were to have a reaction, it's nothing more than a rash (according to her) and my son tells me that it doesn't itch or bother him.  I love my kids and will gladly do what is necessary to protect them, but I'm not comfortable with denying him that which other children get to enjoy - whether it be balloons or candy or icing on a birthday cake.  I try to be consistent with him so there are no problems when he's at her house, but it's frustrating to keep denying him these things and encouraging this charade.  

The court required her, some time ago, to get him tested for food dyes to prove what he was or was not allergic to but she has yet to do this.  But I know for a fact that he is not allergic to most food dyes.  Yet, I don't want him to get mixed signals from his mother and I in this regard.  Allergies are important and not to be downplayed, but also not to be contrived.

Does anyone have any experience with anything like this - where allergies and/or symptoms are fabricated?  Any help is appreciated!

[Pum]

Not to your specific question but some other perspective. If he is allergic to some food dyes but only gets a rash, it is still wise to avoid them. He may develop a worse and worse reaction with repeated exposure. Food dyes and balloons are pretty easy to avoid in the scheme of things (my son needs to avoid all dairy and eggs so birthday cakes are definitely out). I was also allergic to food dyes as a child but grew out of them. It was some reds and a green but I avoided most of them just in case.
You sound like a great Dad but I would pick my battles if I was you. Take care.