My son had many allergies during infancy, sadly we couldn't breastfeed and had a lot of trouble with formula.
I went to the allergist after changing pediatricians (as they were horribly unhelpful) and we did a scratch test. Based on the research I did the tests are 50% accurate for false and positive results, and don't do anything about intolerances, which he had to milk.
The best thing you can do is an elimination diet. This is what I did and what the allergist told me. This way you find the intolerances and the allergies and you can "retest" for free on your own time.
Have them on a diet free of all potential triggers (intolerances and allergies). Look for the common ones, soy, milk, egg, wheat, nuts, etc. Introduce a typical serving if they have had the food before, small amount if they haven't or you suspect a severe reaction. If no reaction the first day, up or give the same amount if started with normal portion size, the next day, till you see a reaction or about day 3 or 4. I can't stress enough how important and convenient it is to keep a journal with all this.
Signs to look for:
Rash around the mouth, usually within seconds to minutes of eating food
eczema on ANY part of body, usually within the next couple days. His was soy, and he would get it on his legs
Congestion (rhinitis) usually within a couple minutes
Diarrhea, usually within 12 hrs or so, a friend of him found out it was chocolate with hers, and it would show the next morning
throwing up usually within hours
stomach aches/gassiness, in little ones, this is hard to tell, but you can usually tell by increased fussiness and lots of tooties
there are more, but these are all I can think of.
Looking back, I think I would skip the testing that I did and just do the elimination diet.