Im kind of glad I wasnt here when this thread was first started as I dont think id have been able to hold back.
First up, allergies are worse now. Theres a whole generation of allergies that havent hit adulthood yet. Which sucks for my son as they dont know how serious cases like his end up. Because it hasnt happened yet, or hasnt happened enough for it to be studied, even on a small scale.
And as for 'is it just in the parents head and they dont really have allergies.' Allergies are under diagnosed.
Just go to the allergy forum and start a thread titled "who else had to fight tooth and nail for my childs allergy to be diagnosed?"
Its not just you that doesnt believe the rate of allergies OP. Its the doctors too.
Thats not because they arent real. Is because allergies have grown at a rate so fast that GP's havent been trained enough in that area.
I have personally found the older doctors are more sceptical and the younger ones are far more interested/open minded. Not that you can ignore my childs allergies because they are life threatening.
Its harder for parents of children with non-life threatening allergies because they are the ones that have to fight to be believed.
One mother I know in RL wasnt believed for such a long time that by the time she was listened to, all the foods her son had been eating had damaged his insides to such an extent he had a stoma fitted and he was fed through that for 3 years.
The GP kept suggesting it was in her head, and perhaps she needed councelling. 
She is now taking the doctor to court. Unlucky for him, her husband is a lawyer.
Anyway, I tell myself not to get irrate at OP's like yours. As before my son had allergies, I had no idea about them. I didnt even know you could get anaphylaxis from a yoghurt. Or be allergic to cucumber, or heat and cold. Or polyester. Etc etc etc
Its all about education and research. And unfortunately allergies beyond our means of education and research.
People hate it when I say this, but I feel a big part to blame is vaccinations.
Not the vaccinations themselves, they are fab. But the amount we give at one time, expecting tiny brand new immune system to cope.
We see specialists in London and they have certainly not poo-pooed my idea and said they are researching this very theory. So it cant all be bullshit.