Conjunctivitis - Symptoms, Causes, Transmission and Treatment

Conjunctivitis is the eye disease caused by inflammation and / or infection of the conjunctiva, the thin membrane that covers part of our eyes. There are several causes of conjunctivitis, including infections, allergies, substance irritations and even neoplasias. The main symptoms of conjunctivitis are red eyes, pain and tearing.


In this article we will explain what is conjunctivitis, what are its main causes, symptoms, forms of transmission and treatment options. Let's also explain the differences between bacterial, viral and allergic conjunctivitis.

The conjunctiva is a thin transparent membrane that covers the frontal region of the eyeball, which is the white part of the eyes which we call the sclera. This membrane also covers the inner portion of the upper and lower eyelids.

The conjunctiva is highly vascularized; those small blood vessels that we can see in our eyes are not exactly in the eyeball, but in the conjunctiva. Under normal conditions, we can see a few blood microvessels, both on the sclera and on the inside of the eyelids.

The photo above shows a healthy conjunctiva. Note that although the vessels are easily identifiable, the sclera is very white and the inside of the eyelids are pink.

When the conjunctiva is inflamed, the situation changes completely. The tiny vessels become very prominent, which causes the characteristic red-eyed aspect of conjunctivitis. The inner lining of the eyelids is no longer rosy and becomes very reddish.

There are basically three types of conjunctivitis:

• Viral conjunctivitis
• Bacterial conjunctivitis
• Allergic conjunctivitis

There are also other forms of conjunctivitis, such as those of neoplastic origin, irritation caused by contact lenses or induced by some substance (shampoo, pool chlorine, smoke, dirt, medicines, etc.). In this article though, we will stick to bacterial, viral and allergic forms.

a) Viral conjunctivitis

It is the most common form of conjunctivitis, usually caused by a virus called Adenovirus. It may be accompanied by other viral symptoms, such as fever, sore throat, and signs of respiratory infection, similar to a cold.

Viral conjunctivitis is extremely contagious, being transmitted through hands contaminated by ocular secretions. Viral conjunctivitis is so contagious that if a patient scratches their eyes and touches an object, other people may become contaminated through it.

Contrary to popular belief, conjunctivitis is not usually transmitted through the air. When you see a person with conjunctivitis, you do not have to run away from it. It is enough that you do not have direct contact with it or with objects handled by it. However, if the infected person also exhibits respiratory symptoms, such as sneezing and coughing, conjunctivitis may be transmitted by contact with these secretions.

The picture of viral conjunctivitis usually begins in one eye, transmitting to the other 24 to 48 hours later. Viral conjunctivitis is self-limiting, healing itself after 7 to 10 days, with no need for specific treatment. The period of contagion usually lasts for as long as the eye remains red.

b) Bacterial conjunctivitis

Bacterial conjunctivitis is much less common than viral conjunctivitis, and is usually caused by one of five bacteria: Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis or Pseudomonas aeruginosa.

The transmission of bacterial conjunctivitis occurs in the same way as viral conjunctivitis, that is, through contact with contaminated secretions. In the bacterial form, however, sneezing and coughing are uncommon and the transmission becomes restricted even in personal contact. Sharing towels and sharing the same bed are high risk situations.

It is worth noting that even though the symptoms of conjunctivitis are almost exclusively ocular, bacteria or viruses can be found throughout the skin and it is possible to contaminate your hands with a simple contact with the infected person's clothing.

Unlike the viral form, bacterial conjunctivitis needs antibiotic eye drops to improve (I'll tell you about the treatment below).

c) Allergic conjunctivitis

Allergic conjunctivitis occurs when the eyes come in contact with any substance in the air that causes irritation. The inflammation of the conjunctiva occurs by an allergic reaction to one of these substances, which may be, for example, pollen, dust, animal hair, mold, etc.

Allergic conjunctivitis is not transmissible. Those who have allergic conjunctivitis need not be absent from school or work. Also it is not necessary to separate towels, cutlery or bed linen.

The allergic form differs from the bacterial and viral form due to intense itching. Often, other allergic symptoms, such as sneezing and nasal coryza, are also present.

A person who lives with me has infectious conjunctivitis (bacterial or viral). How shall we proceed?

• Do not share towels, bedding or cutlery.
• Do not sleep in the same bed.
• Avoid close contact, like hugs and kisses.
• The two of you should wash their hands often.
• Avoid scratching your eyes. If you do, wash your hands before and after.
• Dark glasses help in sensitivity to light but do not prevent transmission.

It is important to know that even carefully, the conjunctivitis, especially the viral ones, are very contagious, so invariably the person who divides the same roof ends up becoming contaminated as well.

The first symptoms of conjunctivitis are usually burning, tearing, feeling of sand in the eyes and "glueing" of the eyelids upon waking. In a short time, the eyes become red and a purulent secretion may appear (excess of remela), mainly in the bacterial form.

Other common symptoms are itchy eyes, pain, swelling of the eyelids and photophobia (strong light intolerance). In general, except for photophobia, there are no other changes in visual ability. The patient feels very uncomfortable in the eyes, but continues to see well.

The conjunctivitis usually begins in one of the eyes, being common the contamination of the other one after a few days.

Many signs and symptoms of conjunctivitis are similar regardless of the cause. The distinction, therefore, is usually made through the recognition of the typical signs and symptoms of each one of the forms.

• The three forms of inflammation of the conjunctiva usually cause ocular secretion. In bacterial conjunctivitis, secretion is typically purulent, whereas in viral and allergic forms it is more aqueous.
• Palpable lymph nodes in the posterior region of the ears are usually present in viral and bacterial forms, but not in the allergic form.
• In viral form, other viral symptoms are usually present, such as coughing, sneezing, sore throat and general malaise.
• The allergic form usually affects both eyes, while infectious forms (viral or bacterial) usually start with one eye and only after a few days reach the other.

During the ophthalmic examination there are also several signs that help the doctor identify the origin of inflammation of the conjunctiva.

Making the differential diagnosis between types of conjunctivitis is not easy. Most non-ophthalmologists do not know how to do it properly. This implies an excessive prescription of eye drops with antibiotics for viral and allergic conjunctivitis, which do not require the same.

The first step for every red-eyed patient is to see an ophthalmologist. First, because several eye diseases, other than conjunctivitis, can cause red eye. Second, because the distinction between viral, allergic or bacterial conjunctivitis is important not only in treatment but also in the indication of temporary withdrawal from school or work.

In general, the eyes are often washed with cold saline solution. Compresses soaked in cold serum also help. In cases of bacterial conjunctivitis, eye drops with appropriate antibiotics should be used for 7 to 10 days.

Never self-medicate. There are specific eye drops for each type of conjunctivitis. Some have anti-inflammatories, other antibiotics, and there are anti-allergic eye drops.

Whoever wears contact lenses should avoid them until symptoms disappear.