All referral forms will ask about allergies. Some will be related to non drug allergies, such as latex gloves, but NICE has specific guidance for drug allergies.
Here are the details
Documenting and sharing information with other healthcare professionals: Recording drug allergy status
1.2.1 Document people's drug allergy status in their medical records using 1 of the following:
'unable to ascertain' (document it as soon as the information is available).
1.2.2 If drug allergy status has been documented, record all of the following at a minimum:
the drug name
the signs, symptoms and severity of the reaction (see recommendation 1.1.1)
the date when the reaction occurred.