Second, let's say you do the ice cube test either on yourself or your child, and nothing happens. You will probably breathe a sigh of relief, thanking your lucky starts that you are not dealing with CU. However, the ice cube test has a false negative rate of about 20%. There is so much more that goes into a diagnosis of CU than just an ice cube. There is history, blood work, different allergy testing and then the ice test. Also, while you are lulled into a false sense of security over CU due to the ice cube test you did at home, the medical community is starting to believe that a negative ice test with a positive history has bigger implications. Specifically they are starting to believe that in this scenario, a genetic form may be at play since genetic forms of CU are harder to illicit a reaction, and almost always negative to an ice cube test.
Third, if I still haven't convince you not to do this test at home, let's think along the lines of a peanut allergy. Let's say you give your child a peanut butter sandwich for lunch. After a few bites, your child is broke out in hives. How would you handle this situation? Would you wait a few hours for the hives to disappear, then give them a spoon and jar of peanut butter letting them go to town eating it to see if the hives appeared again? Of course not! You know the dangers of a peanut allergy thanks to the awareness that this type of allergy has! You would stay away from anything with peanuts and get to a Dr. for the appropriate testing. So why would you do it with CU? It can cause anaphylaxis and anaphylactic shock, just the same as a peanut allergy, so why would you put your child at risk just because it's a different allergy?
When you do the ice test at home you never know what is waiting for you on the other side of the test. Anaphylaxis? Shock? False Negative? Please just put the damn ice cube down and leave it to the professionals.