There are all kinds of food intolerances and food allergies about but one that you may encounter at some time during your life is - wheat intolerance that sometimes leads to blood blisters in the mouth. Once the blisters arrive they have a tendency to enlarge and fill with blood which then extends the blister still further. They can occur anywhere on the soft tissue of the mouth even the uvula (the dangly piece of skin at the back of the throat).
Blood blisters, such as these can be very disturbing. They may continue to grow in size and area travelling until they have either been ‘popped’ or naturally burst. The mouth then may remain very sore for a very long time afterwards. Sometimes, several blood blisters of differing sizes can occur in a cluster.
If you do get recurring blood blisters in the mouth it is wise to firstly see a doctor; secondly read the labels on everything you buy and try not eating wheat for a few weeks (this includes sauces, ready-made meals, many sweets and so on). This may, if you're lucky, be sufficient to cure the problem - if not then possibly wheat might have to be excluded from your diet for a much longer period of time. Point to remember: many food items do not list wheat as an ingredient (including some chocolate bars, liquorice and confectionery) - it is wise to consider looking for wheat free products.
Blisters, blood blisters and ulcers may also be a sign of the onset of Coeliac Disease. Please see the following link for more information: http://kloggers-randomramblings.blogspot.com/2012/01/coeliac-diseasepronounced-see-lee-ack.html