I wanted to share some photos of a couple SPTs that DD had, in case anyone is curious what the test looks like.
First, here is a good website describing the process. When you get a skin prick test, you look for a wheal (hive) and flare (red blotch surrounding the hive) to determine a positive or negative. Normally you are given one prick containing histamine for a positive control, and a negative control spot containing nothing (saline, perhaps?) If the other test spots are the same size or larger than the histamine control, you have a positive result. The link above also compares the wheal size to the old class scale that some allergists use (4+ being the most severe allergy.)
So here in the pictures, you can see how they mark each area to be "pricked" with a pen. This particular allergist has a tool that can hold 8 needles at once, so they label each group of pricks with a number. Then the allergens are applied to the skin and a needle pricks or scratches the spot (sometimes this is done all in one step) and you sit and wait anwhere from 5-20 minutes. Here, DD has just had the pricks done, and she is already showing some reactions. The upper spots are just red from being poked, but few are actually positive results. The lower ones however, are definitely positive.
On the bottom right corner in this picture you can see the positive(+) and negative(-) control spots. Just above those (if you're curious) is goat's milk, and you can see that it's quite a bit larger than the positive control, so it's a very clear positive (allergic) result, as are the ones on the lower left.
Just to give another example, here is a SPT from a couple years ago. On the right-hand side, we have 3 positive results. The top and bottom one have very large wheals with just slightly larger flares, and the middle has a smaller wheal with a large flare.