Please note that intolerances are very real. They may look fussy or faddy, but the person suffering from them has to alter their life dramatically to avoid the impact. I can rarely eat out or get takeaways, people are less apt to invite us over for meals and to be honest, I have had to become quite hesitant to eat anything I have not prepared myself at home.
DS and I are both dairy intolerant, but show no sign of dairy allergy (skin prick tests at multiple allergists, NHS and private). With DS, who is 5, butter in single biscuit makes him seem like he has ADHD, stops him sleeping, makes him clumsy and he then appears to be autistic (what CAMHS calls an "autistic defence"). Birthday parties and school dinners are a nightmare, but we seem to have got it under control now. A tiny bit of dairy and he is a different (very challenging) child.
With me, I get breathless, clammy, nauseous and bloated with extremely rank farts. Depending on the quantity consumed, and how long I've had to hold the rapidly building farts in, I then get severe cramps and explosive diarrhoea. I also get sinusitis within a few hours. Can't move my head around as it feels like someone is bashing it with a hammer.
You wouldn't know that though as I am very, very careful to avoid getting ill and learned to hide my (uncomfortable and antisocial) symptoms from a young age.
Since having my son, I have also developed a wheat intolerance, again not picked up by allergy testing. If I eat anything with wheat in it (soya sauce, gravies, crumbs from the toaster) my joints swell, I get breathless, clumsy, forgetful, and psoriasis appears on my scalp and elbows. It takes a few days to return to normal. It is debilitating, but again, not something that the medical profession is able to clinically diagnose.
Yes, some people can be fussy, but please do not discount the impact that food can have on people's quality of life. I do occasionally eat in restaurants, with friends or for special events, and even when I am very careful about what and how I order, I usually end up suffering afterwards. If you don't have intolerances yourself, then count yourself lucky and try to be more compassionate.