I have been frequently I ever know what it is like to have allergies? No, not allergic rhinitis (hayfever). My wife has severe allergies, as do most of my family. So I have lived with the sneezing, red eyes, nose blowing, and need for (OTC and prescription) meds my entire life.
Now, with regard to itchy skin disorders, I think I have direct experience and can understand how people feel. First, occasionally get a fine, red, itchy rash on my lower legs. It has been bad enough to interrupt my sleep and my work during the day for weeks. Relief comes from topical calcineurin inhibitors, a class of prescription medications available for eczema. Antihistamines do not help.
I also get very large reactions from mosquito bites. A single bite with no scratching will swell up to a red, raised bump of 2-3 cm, that severely itches and lasts 7-10 days. I've learned not to scratch because I get bruising and sometimes the skin breaks open, which leads to oozing. When I'm bit on my face, it looks like I've been in a fight. Needless to say, I really don't like mosquito bites. Been like this my entire life. Antihistamines don't help. I use Vicks and OTC hydrocortisone cream on top to stop itching. When the itching is severe, I have to get a medium strength steroid cream or Doxepin cream for relief.