My husband is allergic to onion and anything in the same family (leeks, spring onions, shallots, chives etc.) and can only tolerate very small amounts of garlic. Plus he hates hot and spicy food. I substitute onion with celery where applicable, and sometimes use stock powder for flavour, however I am wondering if you have any suggestions as to what I can use as an onion or garlic substitute in savoury recipes?
Although allium allergies are quite rare, they are frustrating as most cuisines use onions and/or garlic as a base for savoury dishes. As well as using just celery in dishes, you could use a combination of celery and carrot or celery, and green (bell) pepper to add more base flavour to your dishes. These reflect the ingredients of mirepoix (onion, celery and carrot) in French cooking and the trinity (onion, celery and green pepper) in Cajun cooking. Fennel is in the same family as celery and carrot and can also be used if you like a mild anise flavour.
Asafoetida (also known as giant fennel or hing) is also sometimes used as a substitute for garlic in cooking. It is used in Indian and Middle eastern cooking and you are most likely to find it in powdered form in specialist stores or on-line. Unfortunately it has quite an unpleasant smell in its uncooked form (one of the common names for asafoetida is devil's dung) so should be kept in a well-sealed jar or container. However, this smell disappears on cooking and leaves a flavour which is said to be similar to sauteed onion or garlic.