Dylan's scratch test was done on his back - we were doing multiple allergens (dairy, egg white, egg yolk, peanut, citrus, dust mite, mustard, I think that was it) and we couldn't do it on his arms. I basically had him in a bear hug facing me (so chest to chest, with his legs wrapped around my waist) and I held him tight, squirming and crying, while they did the scratch
I absolutely hated it. Then we got the results (which were surprising; a HUGE result for peanut, and then the positive egg result that was unexpected) and the allergist sent us for blood tests because sometimes children with eczema give a false positive result on scratch tests because of the sensitivity of their skin
The blood tests weren't much better, but were so much FASTER. We are getting him retested at age 3 to see if there is any value in doing a food challenge, and I will be doing blood tests only.
Having said that... If you're only doing a single scratch for dairy (or dairy and fish) it would probably go much more easily because it would be quick and done. One or two scratches are over before you know it, Dylan's test took a few minutes because she kept switching lancets, then needed to add more of the peanut stuff, etc.
Although I would like him tested for fish as well, as my brother has an anaphylactic fish allergy and we're afraid of offering it to LO...
I don't know if it eases your milk at all, but *specific* allergies are not inherited - only the tendency to be allergic. Allergies, asthma, and eczema are all connected - so if you have asthma and an allergy to peanuts, your lo might develop eczema or an allergy to tomato. I have tons of environmental and animal allergies, and my DH gets hayfever, and Dylan has multiple food allergies and an allergy to dog saliva. So your brother being anaphylactic to fish doesn't at all increase the likelihood that your ds will be allergic to fish - but it does increase the likelihood that he will be allergic to *something* (or develop asthma/eczema), kwim? Having said all of that - trust your mommy instinct. Offer him some fish in the car in the parking lot of the ER if that's what it takes for you to feel safe - I have heard of some moms doing food challenges in that way!