Hay Fever and Dry Eye

Spring is getting a little closer, and more people are visiting with itchy eyes.

The “conjunctiva,” the transparent membrane that runs from the inside of the upper and lower eyelids to the white of the eye, has many blood vessels and lymphatic vessels and is therefore a tissue that becomes inflamed very easily.

“Mast cells” are always lurking inside the conjunctiva.

* They are called mast cells (literally “fat cells”) because they look swollen under the microscope.

The surface of the eye is in contact with the outside world, and all sorts of fine particles constantly come in and are cleared away.

These particles become antigens (allergens) and cause allergic conjunctivitis.

For many people, the strong itching also lowers productivity.

Among allergic conjunctivitis, the types that fall under hay fever are

seasonal allergic conjunctivitis / perennial allergic conjunctivitis.

In spring, many fine particles, including Japanese cedar pollen, fly in and get onto the surface of the eye.

* Others include orchard grass, Japanese cypress, ragweed, mugwort, and so on

Through white blood cells that have taken in the antigen, mast cells burst and release a chemical called histamine.

Histamine sends itch signals from the spinal cord to the brain via pruriceptors (itch receptors).

Allergic inflammation is classified into two reactions.

Immediate allergic reaction (occurs right away): “seasonal allergic conjunctivitis” (SAC, Seasonal Allergic Conjunctivitis)

Five minutes after the antigen enters, the histamine released from mast cells into the tears peaks, and symptoms such as itching are known to last 30–40 minutes.

Delayed allergic reaction (continues for a long time): “perennial allergic conjunctivitis” (PAC, Perennial Allergic Conjunctivitis)

6 to 72 hours after the antigen enters:

Inflammatory cells (basophils, eosinophils, T lymphocytes, neutrophils) come out of blood vessels and begin gathering in the conjunctiva, and release cytokines (biologically active substances) that worsen the inflammation.

Most patients who visit saying “my eyes itch” are thought to be having both reactions. Inflammation of the conjunctiva may also leave the eyelids “swollen.”

In ophthalmology long ago, a vasoconstrictor called Vasocon was apparently used for itching.

Today, the main treatment policies are as follows.

(1) Prevent histamine from being released / prevent histamine from acting

Alesion®, Patanol®, Intal®, Livostin®, Rizaben® eye drops, etc.

* Among the above, using the eye drops before itching symptoms appear is also known to be effective.

(2) Suppress the inflammation itself (steroids)

0.1% Flumetholon®, Rinderon® eye drops, etc.

* Care is needed for side effects such as increased eye pressure.

○ About dry eye:

In dry eye (an unstable tear film on the surface of the eye), the antigen becomes concentrated, so the symptoms of allergic conjunctivitis get worse.

Dry eye

In people whose allergic conjunctivitis has worsened, my impression is that the tear film is also often unstable.