Dr Chandima Jeewandara, Director, Institute of Allergy and Immunology and Cell Biology, University of Sri Jayewardenepura had made this explanation regarding allergies, to the
BBC news service

It is not advisable to get vaccinated if you had a severe allergic reaction (anaphylaxis) to any of the ingredients in the vaccine and also people who develop severe anaphylaxis after the first dose should not take the second dose.

People with a history of severe allergies (anaphylaxis) to vaccines or non-vaccine-related allergens, such as food, pets, snake venom, environmental contaminants, or rubber products. ) and people who are allergic to certain medications (eg aspirin, paracetamol, ibuprofen, amoxicillin) or have a family history of anaphylaxis can also be vaccinated.

If you have had an immediate allergic reaction (severe or non-severe) during a vaccine treatment, ask your doctor if it is appropriate for you to receive a COVID-19 vaccine. Your doctor will help you determine if the vaccine is safe for you. Even after receiving the vaccine, you will be monitored for allergies within 15 minutes (which is very rare). So do not be afraid to get vaccinated.