Allergic to Avocado!

I've been weaning Theo since 4 months (he's 5 months 1 week now) and on Monday I tried avocado for the first time. He loved it and ate loads but after an hour or so I noticed he was covered in a red blotchy rash and was really worried! I took him to the doctor and he said its definitely a reaction to something he ate or drank. Well the avocado was the only thing he'd eaten in the previous few days that he'd not had before so it must have been that! Poor little mite! Luckily he didn't seem too bothered by it and it's cleared up now. A shame though as he liked it so much and also it's an easy one as it doesn't have to be cooked. Oh well. He's not fussy though and he's liked most things I've given him - only thing he didn't like was parsnip which I've tried twice and both times he's wretched!!!