Hi fellow garlic free folks.  I have a number of food allergies in addition to celiac disease (not uncommon to have both) and so I do a LOT of cooking at home.  For over a year I was going progressively blind.  First I would be partially blind for a few hours once a month, then once a week and then every day I would be mostly blind for few hours each day.  The opthamologist and the neurologist could find nothing wrong.  Finally a naturopath suggested allergy testing and I discovered that in addition to my celiac disease I had several allergies including garlic.  I immediately cut all the allergens out of my diet and felt so much better including no more blindness episodes.  About two months later I accidentally ate garlic and a few hours later I was going blind.  Turns out it was scotoma which many people with migraines get.  The garlic triggered a virtually painless migraine. 

Now I use Shallot salt (from Penzey's) and fresh shallots in place of garlic.  You get a similar taste without the reaction.  At least for me, the shallots are more like onions.  The shallot salt is great for "garlic" bread and it tastes great on popcorn. 

One other quick note.  FDA laws require a food manufacturer to list garlic as a separate ingredient UNLESS it is in a flavoring (aka an extractive.)  It is NOT included in "spices."  So if you see a label with no garlic listed but with natural flavors as an ingredient, beware!  If there is no garlic listed but spices are, you should be fine.  If you are worried, call.  Most companies have been great to me, except Heinz which required a doctor's note to reveal any of their secret ingredients.  Later a customer service person told me that I should assume that all Heinz products have garlic in them.   Good luck.