Patient History of Food Allergy and Allergic Diseases
With the patient history, the physician is attempting to determine the likelihood that the patient has a food-induced allergic disorder on the basis of the symptoms, the timing of the reaction, and the food suspected of causing the reaction.
A comprehensive patient history should include:
- Suspected foods
- Time interval from ingestion of the food to onset of symptoms
- Quantity of food needed to elicit the reaction
- The most recent occurrence
- The number of occasions on which the reactions have occurred
- Association of additional factors such as exercise and concurrent medication ingestion
- Family history of allergic diseases
- Whether they were breast or formula fed
- Age of introduction of solids / weaning
- Any infections at the time of the reaction
It is important for the clinician to gather the following:
Time interval from ingestion of the food to onset of symptoms This can be a valuable indication of whether the mechanism might involve
IgE antibodies.
IgE-mediated reactions often occur within five minutes and mostly within an hour. Reactions that are not mediated by
IgE usually take a longer period to develop, up to 24 hours or more in some cases.
Quantity of food required to elicit the reaction Another indication of whether IgE may be involved in the mechanism of
food allergy is provided by the amount of food eliciting a reaction. Typically IgE-mediated reactions can be provoked by very minimal amounts of food. In the non-IgE reactions a larger amount of food (perhaps 100-200ml of milk) is usually ingested before a reaction is provoked.
Number of occasions on which the reaction has occurred It is important to find out whether the reaction was an isolated incident or whether food-related symptoms have been reproduced on multiple occasions.
Association of additional factors Sometimes other factors can influence a reaction to a particular food, for example exercise. This is seen in disorders such as food-induced
anaphylaxis. Other patients will experience the food allergic symptoms only when taking certain medications such as aspirin or non-steroidal anti-inflammatory agents.
During the consultation it is also important to gather several other pieces of information such as:
Whether the child was breast or bottle-fed Certain conditions are more or less likely depending on the feeding method used. A child who first displayed symptoms whilst being exclusively breastfed is more likely to be very sensitive / multiply allergic.
Are medications being taken Certain medications, such as
antihistamines, can interfere with diagnostic tests. Some medicines may contain ingredients, either actives or excipients, which are causing or may contribute to symptoms.
Past and current treatments Informs the physician about which treatments have proved to be effective in the past and might allow certain diagnoses to be ruled out.
Family history of allergic diseases This is the single most important predictor of whether a child has a food allergy. 30% of food allergic infants have a parent with atopic disease, whereas 60% of infants will be food allergic if both parents are atopic.