Local lyophylized food extracts are available useful in skin prick test and atopy patch test to confirm food allergy. However, the investigators want to know the duration that the investigators can keep the extracts for the usage in this purpose.

Food allergy incidence increases world wide. The diagnosis mostly depends on history. Skin prick test and atopic patch test are useful in finding the causative foods in some cases. The local food extracts have been shown to be at least as effective as commercial ones. From previous study the investigators keep the extract at 2-8 degree Celsius for 1-3 months for the usage. The investigators want to evaluate the duration that the extracts are still useful in diagnosis food allergy

Inclusion Criteria:

• Positive skin prick test to one of the food (milk, egg, soy, wheat, seafood)

Exclusion Criteria:

• Chronic diseases such as heart disease, liver, renal and severe sepsis
• Severe allergic symptoms such as anaphylaxis
• Extensive skin rashes
• Pregnancy

Food allergy cases aged 3-18 years old.