The move from winter to spring is widely celebrated: few can help but have their spirits lifted by the sight of trees coming into leaf and flowers starting to bloom.
But the advent of warmer weather also brings with it a rise in pollen levels, which can trigger hay fever in those predisposed to the condition.
This week Asha Fowells runs through some of the more common ocular symptoms of this disorder: seasonal allergic conjunctivitis and dry eye syndrome
The term allergic conjunctivitis refers to inflammation of the conjunctiva of the eye as a result of a hypersensitivity reaction.
In hay fever, the reaction is a type I hypersensitivity, in that contact with the allergen causes immediate degranulation of mast cells, which leads to histamine release.
As well as causing itchiness, this leads to dilatation and increased permeability of the blood vessels in the conjunctiva, which in turn results in redness and oedema.
It is worth noting that the reaction behind allergic conjunctivitis – whether seasonal or perennial – is very different to that of contact dermatoconjunctivitis, which can occur as a result of eye drop or cosmetic use or following chemical exposure.
This results in a type IV hypersensitivity, which develops 24-48 hours after contact with the allergen and is not the result of mast cell degranulation and histamine release; it is a much stronger inflammatory response.
Giant papillary conjunctivitis – resulting from a reaction to contact lenses or stitches used or prostheses fitted during eye surgery – is a mixture of type I and IV reactions.
It is difficult to put a figure on the number of people who suffer from seasonal allergic conjunctivitis because so many of them self-treat, but it is certainly the most common form of allergic conjunctivitis.
It is relatively easy to diagnose, as both eyes are usually affected and it recurs each year at around the same time.
If the allergen is tree pollen, symptoms start in spring, whereas those sensitive to grass pollen will start to suffer in early summer, and those allergic to weeds and fungal spores will notice an issue in late summer.
Anyone can be affected by seasonal allergic conjunctivitis but there are some factors that predispose individuals to the condition, namely having a history of, or current allergic disease, such as hay fever, asthma, eczema or food or drug allergy, or having a first degree relative who is atopic.
The main presenting symptoms have already been touched upon – itchy eyes, redness and watering – and are often accompanied by other allergy symptoms, for example, sneezing and a runny or blocked nose.
It differs from infective conjunctivitis in that the gritty or burning sensation is absent, as is the sticky discharge experienced by many, particularly first thing in the morning, nor are the lymph nodes enlarged.
Join us again tomorrow as we explore treatment options for seasonal allergic conjunctivitis.