999 Reasons

Infants 

6-8 MONTHS: Solid foods should be introduced slowly, one at a time to check for allergies, usually around the 6 month mark. Your baby should be able to hold it's head up and sit alone before you start solids. You can tell when many babies are ready when they are curious and appear to be more hungry than usual and the tongue does not protrude as much, allowing for a more effective chewing motion. Start with just a small amount (1/2 a tablespoon) of gluten free rice cereal with formula or breast milk once a day and slowly build up the amount till the baby gets used to their new diet. You will know when your baby is full when they start to spit out the food. 

Moving on to pureed fruits and vegetables one at a time each for four days, when your child seems to be eating confidently is the most effective way to get them used to the new tastes and textures. Foods such as sweet potato, pear, apples, bananas and carotts are all good starting points but make sure to continue with around three supplementary breastmilk or formula feeds a day until they are one year old. 

8-12 MONTHS: By around 8 months your child should be eating around three full meals a day. You can now offer chopped and finger foods and start letting them hold their own spoon (if you can tolerate the mess!). Small amounts of protein such as chicken, tofu and lean mince can be introduced with their vegetables too. In general, foods such as honey, shellfish, strawberries, peanut butter, citrus, egg whites and cow's milk should be avoided until the child is at least 12 months. 

If there are allergies in the family, extra precautions should be taken when introducing new foods. The American College of Allergy, Asthma and Immunology says that in families with allergies that pediatricians and allergists should cautiously individualize the introduction of solids into the infants' diet. With assessed risk of allergy, the optimal age for the introduction of selected supplemental foods should be 6 months, dairy products 12 months, hen's egg 24 months, and peanut, tree nuts, fish, and seafood at least 36 months. For all infants, complementary feeding can be introduced from the sixth month, and egg, peanut, tree nuts, fish, and seafood introduction require caution. Foods should be introduced one at a time in small amounts. Mixed foods containing various food allergens should not be given unless tolerance to every ingredient has been assessed.'¹ 1. Ann Allergy Asthma Immunol. 2006 Jul;97(1):10-20; Food allergy and the introduction of solid foods to infants: a consensus document. Adverse Reactions to Foods Committee, Fiocchi A, Assa'ad A, Bahna S.

If you are at all concerned, check with your pediatrician or GP to make sure you are getting all the nutrients your baby needs.