Yvonne says Liam has learned to be "really disciplined and totally organised" with food and thus everything in his life.
His health conditions have also resulted in him having "immense empathy" for others who face hurdles in life.
Liam says he has simply "the best parents".
His mum, and dad Ian, equally share all the special cooking and baking he needs. Liam is among an estimated one in 10 children in New Zealand who is estimated to have a food allergy and an increasing number of those affected have multiple food and/or environmental allergies andasthma.
This week is Allergy Awareness Week (May 20-26) and the national charity Allergy New Zealand is keen to highlight the increasing prevalence of allergies.
Dr Rohan Ameratunga, an adult and paediatric allergy specialist and clinical immunologist, says more research is crucial to understanding why allergies afflict so many. But in today's economic climate, funding for such Kiwi research remains tough to get.
There is no cure for allergies and complete avoidance of a particular allergen is the only way to prevent an allergic reaction.
The doctor says there are some theories why allergies exist, such as society being too clean and children not being exposed to enough bacteria, to changing diets, to people not getting enough exposure to vitamin D and to increasing environmental pollutants. The doctor says Kiwis need to have empathy for those who suffer from allergies - and not think sufferers are just fussy with food.
"It's important to put yourself in the shoes of the child, or the parents trying desperately to keep their child safe," he says.
He says the most common allergies are linked to eggs, milk, peanuts, wheat, and soy, while as people got older shellfish and tree nuts could be included.
For children, eczema commonly starts on the face and diaper area and if it persists to later life, it can end up on places such as the elbows, knees, palms and soles. Ameratunga says if anyone suspects an allergy they should see a GP and will likely have a scratch or blood test to discover what they are allergic to.
Top five ways to get your kids to eat more veges:
1. Dress it up: Make a face with peas for eyes, a cherry tomato for a nose, red pepper for a mouth and mashed potato for hair. Make vegetables fun.
2. Blind them with science: The science of taste suggests 10 tastes is all it takes to like a new food; tell your kids: "You don't have to eat it, you just have to try it."
3. Try their patience: Offer the same vegetable in different ways - blanched, fried, raw, with sauce, without sauce - they are bound to like one of them eventually.
4. Make it juicy: Add a few vegetables when you're making fresh fruit juice, such as cucumber and celery to apple juice.
5. If all else fails, get sneaky: Hide vegetables in foods they like, such as chocolate cupcakes with added mashed broccoli or cauliflower, or meatloaf with grated carrot.
Food matters
* See allergy.org.nz for information or to financially support the charity.
* Join Allergy New Zealand on facebook.com/allergy.nz and online allergy support groups.
* Anyone can register to attend a Food Monsters seminar at the Parenting Place, 300 Great South Rd, Greenlane, Auckland, on May 26. Register through allergy.org.nz. The seminar is for parents of children who are restricted in what they can eat.