Hi hannah louise,
How are you? Do you have a family history of allergies? Allergy or hypersensitivity is a reaction of your immune system to something that does not bother most other people.. Your gardening may have exposed you to something that triggered your immune system. Before, it is believed that the reason allergies develop is through genetics. However, with more people experiencing allergies, environmental factors are also considered. Substances that often cause reactions are: pollen, dust mites, mold spores, pet dander, food, insect stings or even medicines Allergies can cause a runny nose, sneezing, itching, rashes, and/or swelling, just like what you had. To confirm this, you could visit your doctor for allergy skin test. You can learn more about this through this link: http://www.mayoclinic.com/health/allergy-tests/AA00051
I hope this helps. Take care and keep us posted.