Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Its symptoms include excessive watering and itching. The infection usually begins with one eye, but may spread easily to the other.

Viral conjunctivitis shows a fine, diffuse pinkness of the conjunctiva, which is easily mistaken for the ciliary infection of iris (iritis), but there are usually corroborative signs on microscopy, particularly numerous lymphoid follicles on the tarsal conjunctiva, and sometimes a punctate keratitis.

Allergic conjunctivitis is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. Allergens differ among patients.

Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), swelling of the conjunctiva, itching, and increased lacrimation (production of tears). If this is combined with rhinitis, the condition is termed "allergic rhinoconjunctivitis". The symptoms are due to release of histamine and other active substances by mast cells, which stimulate dilation of blood vessels, irritate nerve endings, and increase secretion of tears.

Neonatal conjunctivitis by definition presents during the first month of life. It may be infectious or non infectious. In infectious conjunctivitis, the organism is transmitted from the genital tract of an infected mother during birth or by infected hands.

- Pain and tenderness in the eyeball.

- Conjunctival discharge: purulent, mucoid or mucopurulent depending on the cause.

- Conjunctiva shows hyperaemia and chemosis. Eyelids are usually swollen.

- Corneal involvement (rare) may occur in herpes simplex ophthalmia neonatorum.

Untreated cases may develop corneal ulceration, which may perforate resulting in corneal opacification and Staphyloma formation.

Among the signs of subacute bacterial endocarditis are:

- Malaise

- Weakness

- Excessive sweat

- Fever

The conjunctiva is a thin membrane that covers the eye. When an allergen irritates the conjunctiva, common symptoms that occur in the eye include: ocular itching, eyelid swelling, tearing, photophobia, watery discharge, and foreign body sensation (with pain).

Itching is the most typical symptom of ocular allergy, and more than 75% of patients report this symptom when seeking treatment. Symptoms are usually worse for patients when the weather is warm and dry, whereas cooler weather with lower temperatures and rain tend to assuage symptoms. Signs in phlyctenular keratoconjunctivitis include small yellow nodules that develop over the cornea, which ulcerate after a few days.

A study by Klein et al. showed that in addition to the physical discomfort allergic conjunctivitis causes, it also alters patients' routines, with patients limiting certain activities such as going outdoors, reading, sleeping, and driving. Therefore, treating patients with allergic conjunctivitis may improve their everyday "quality of life."

"Other infections include:"

- "Closed-space infections of the fingertips, known as paronychia."

Blepharitis is characterized by chronic inflammation of the eyelid, usually at the base of the eyelashes. Symptoms include inflammation, irritation, itchiness, a burning sensation, excessive tearing, and crusting and sticking of eyelids. Additional symptoms may include visual impairment such as photophobia and blurred vision. Symptoms are generally worse in the mornings and patients may experience exacerbation and several remissions if left untreated. It is typically caused by bacterial infection or blockage of the meibomian oil glands. Diseases and conditions that may lead to blepharitis include: rosacea, herpes simplex dermatitis, varicella-zoster dermatitis, molluscum contagiosum, allergic dermatitis, contact dermatitis, seborrheic dermatitis, staphylococcal dermatitis, demodicosis (Demodex), and parasitic infections ("e.g.", Demodex and Phthiriasis palpebrarum).

The parasite, "Demodex folliculorum" ("D. folliculorum"), causes blepharitis when the parasite is present in excessive numbers within the dermis of the eyelids. These parasites can live for approximately 15 days. The parasites (both adult and eggs) live on the hair follicle, inhabiting the sebaceous and apocrine gland of the human lid. Direct contact allows this pathogen to spread. Factors that allow this pathogen to multiply include hypervascular tissue, poor hygienic conditions, and immune deficiency. In treating Blepharitis caused by "D. folliculorum", mechanical cleaning and proper hygiene are important towards decreasing the parasites numbers.

Associated Symptoms:

- Watery eyes - due to excessive tearing.

- Red eyes - due to dilated blood vessels on the sclera.

- Swollen eyelids - due to inflammation.

- Crusting at the eyelid margins/base of the eyelashes/medial canthus, generally worse on waking - due to excessive bacterial buildup along the lid margins.

- Eyelid sticking - due to crusting along the eyelid margin.

- Eyelid itching - due to the irritation from inflammation and epidermis scaling of the eyelid.

- Flaking of skin on eyelids - due to tear film suppressed by clog meibomian glands.

- Gritty/burning sensation in the eye, or foreign-body sensation - due to crusting from bacteria and clogged oil glands

- Frequent blinking - due to impaired tear film from clogged oil glands unable to keep tears from evaporating.

- Light sensitivity/photophobia

- Misdirected eyelashes that grow abnormally - due to permanent damage to the eyelid margin

- Eyelash loss - due to excessive buildup of bacteria along the base of the eyelashes.

- Infection of the eyelash follicle/sebaceous gland (hordeolum)

- Debris in the tear film, seen under magnification (improved contrast with use of fluorescein drops)

Chronic blepharitis may result in damage of varying severity and, in the worst cases, may have a negative effect on vision. This can be resolved with a proper eyeglass prescription. Long-term untreated blepharitis can lead to eyelid scarring, excess tearing, difficulty wearing contact lenses, development of a stye (an infection near the base of the eyelashes, resulting in a painful lump on the edge of the eyelid) or a chalazion (a blockage/bacteria infection in a small oil glands at the margin of the eyelid, just behind the eyelashes, leading to a red, swollen eyelid), chronic pink eye (conjunctivitis), keratitis, and corneal ulcer or irritation. The lids may become red and may have ulcerate, non-healing areas that may lead to bleeding. Blepharitis can also cause blurred vision due to a poor tear film. Tears may be frothy or bubbly, which can contribute to mild scarring along the eyelids. Symptoms and signs of blepharitis are often erroneously ascribed by the patient as "recurrent conjunctivitis".

Staphylococcal blepharitis and Posterior blepharitis or "rosacea-associated" blepharitis Symptoms

Symptoms include a foreign body sensation, matting of the lashes, and burning. Collarette around eyelashes, a ring-like formation around the lash shaft, can be observed. Other symptoms include loss of eyelashes or broken eyelashes. The condition can sometimes lead to a chalazion or a stye. Chronic bacterial blepharitis may also lead to ectropion. Posterior blepharitis or "rosacea-associated" blepharitis is manifested by a broad spectrum of symptoms involving the lids including inflammation and plugging of the meibomian orifices and production of abnormal secretion upon pressure over the glands.

Allergic conjunctivitis is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. Although allergens differ among patients, the most common cause is hay fever. Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), edema (swelling) of the conjunctiva, itching, and increased lacrimation (production of tears). If this is combined with rhinitis, the condition is termed allergic rhinoconjunctivitis.

The symptoms are due to release of histamine and other active substances by mast cells, which stimulate dilation of blood vessels, irritate nerve endings, and increase secretion of tears.

Treatment of allergic conjunctivitis is by avoiding the allergen ("e.g.", avoiding grass in bloom during "hay fever season") and treatment with antihistamines, either topical (in the form of eye drops), or systemic (in the form of tablets). Antihistamines, medications that stabilize mast cells, and nonsteroidal anti-inflammatory drugs (NSAIDs) are generally safe and usually effective.

"Staphylococcus" is a genus of Gram-positive bacteria that can cause a wide variety of infections in humans and other animals through infection or the production of toxins.

Staphylococcal toxins are a common cause of food poisoning, as they can be produced in improperly-stored food. Staphylococci are also known to be a cause of bacterial conjunctivitis. "Staphylococcus aureus" can cause a number of different skin diseases. Among neurosurgical patients, it can cause community-acquired meningitis.

In the acute stage of the disease, a catarrhal conjunctivitis is present, with signs of ocular pain, usually blepharospasm, increased lacrimation, and photophobia. Miosis is also usually present. After a few days, this will progress to a keratitis and iridocyclitis. Other ocular problems may also occur, including conjunctival and corneal oedema, and aqueous flare.

After an acute flare-up, no clinical signs of disease may be seen for a prolonged period, which can vary from a few hours to a few years. With frequent acute incidents, though, additional clinical signs may be seen, including anterior and posterior synechiae, poor pupillary responses, cataracts, and a cloudy appearance to the vitreous humour.

Allergic rhinitis may be seasonal or perennial. Seasonal allergic rhinitis occurs in particular during pollen seasons. It does not usually develop until after 6 years of age. Perennial allergic rhinitis occurs throughout the year. This type of allergic rhinitis is commonly seen in younger children.

Allergic rhinitis may also be classified as Mild-Intermittent, Moderate-Severe intermittent, Mild-Persistent, and Moderate-Severe Persistent. Intermittent is when the symptoms occur 4 days/week and >4 consecutive weeks. The symptoms are considered mild with normal sleep, no impairment of daily activities, no impairment of work or school, and if symptoms are not troublesome. Severe symptoms result in sleep disturbance, impairment of daily activities, and impairment of school or work.

Keratoconjunctivitis is inflammation ("-itis") of the cornea and conjunctiva.

When only the cornea is inflamed, it is called "keratitis"; when only the conjunctiva is inflamed, it is called "conjunctivitis".

There are several potential causes of the inflammation:

- Keratoconjunctivitis sicca is used when the inflammation is due to dryness. ("Sicca" means "dryness" in medical contexts.) It occurs with 20% of rheumatoid arthritis patients.

- The term "Vernal keratoconjunctivitis" (VKC) is used to refer to keratoconjunctivitis occurring in spring, and is usually considered to be due to allergens.

- "Atopic keratoconjunctivitis" is one manifestation of atopy.

- "Epidemic keratoconjunctivitis" is caused by an adenovirus infection.

- "Infectious bovine keratoconjunctivitis" (IBK) is a disease affecting cattle caused by the bacteria "Moraxella bovis".

- "Pink eye in sheep and goat" is another infectious keratoconjunctivitis of veterinary concern, mostly caused by "Chlamydophila pecorum"

- "Superior limbic keratoconjunctivitis" is thought to be caused by mechanical trauma.

- "Keratoconjunctivitis photoelectrica" (arc eye) means inflammation caused by photoelectric UV light. It is a type of ultraviolet keratitis. Such UV exposure can be caused by arc welding without wearing protective eye glass, or by high altitude exposure from sunlight reflected from snow ("snow blindness"). The inflammation will only appear after about 6 to 12 hours. It can be treated by rest, as the inflammation usually heals after 24–48 hours. Proper eye protection should be worn to prevent keratoconjunctivitis photoelectrica.

In documented BPF cases, the symptoms include high fever (101.3 degrees F or higher), nausea, vomiting, severe abdominal pain, septic shock, and ultimately death. A history of conjunctivitis 30 days prior to the onset of fever was also present in the documented BPF cases.

The physical presentation of children infected with BPF include purpuric skin lesions affecting mainly the face and extremities, cyanosis, rapid necrosis of soft tissue, particularly the hands, feet, nose, and ears. Analysis of the fatalities due to BPF showed hemorrhage in the skin, lungs, and adrenal glands. Histopathology showed hemorrhage, intravascular microthrombi and necrosis in the upper dermis, renal glomeruli, lungs, and hepatic sinusoids.

The bacteria invade the lacrimal glands of the eye, causing keratitis, uveitis, and corneal ulceration. Cattle show signs of pain, increased lacrimation, excessive blinking, and conjunctivitis. More severe cases may show systemic signs such as anorexia and weight loss. Chronic untreated cases can become blind. Diagnosis is usually based on the clinical signs, but the bacteria can be cultured from lacrimal swabs, or visualised on smears of lacrimal secretions.

Allergic rhinitis, also known as hay fever, is a type of inflammation in the nose which occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, itchy, and watery eyes, and swelling around the eyes. The fluid from the nose is usually clear. Symptom onset is often within minutes following exposure and they can affect sleep, the ability to work, and the ability to concentrate at school. Those whose symptoms are due to pollen typically develop symptoms during specific times of the year. Many people with allergic rhinitis also have asthma, allergic conjunctivitis, or atopic dermatitis.

Allergic rhinitis is typically triggered by environmental allergens such as pollen, pet hair, dust, or mold. Inherited genetics and environmental exposures contribute to the development of allergies. Growing up on a farm and having multiple siblings decreases the risk. The underlying mechanism involves IgE antibodies attaching to the allergen and causing the release of inflammatory chemicals such as histamine from mast cells. Diagnosis is usually based on a medical history in combination with a skin prick test or blood tests for allergen-specific IgE antibodies. These tests, however, are sometimes falsely positive. The symptoms of allergies resemble those of the common cold; however, they often last for more than two weeks and typically do not include a fever.

Exposure to animals in early life might reduce the risk of developing allergies to them later. A number of medications may improve symptoms including nasal steroids, antihistamines such as diphenhydramine, cromolyn sodium, and leukotriene receptor antagonists such as montelukast. Medications are, however, not sufficient or are associated with side effects in many people. Exposing people to larger and larger amounts of allergen, known as allergen immunotherapy, is often effective. The allergen may be given as injections just under the skin or as a tablet under the tongue. Treatment typically lasts three to five years after which benefits may be prolonged.

Allergic rhinitis is the type of allergy that affects the greatest number of people. In Western countries, between 10–30% of people are affected in a given year. It is most common between the ages of twenty and forty. The first accurate description is from the 10th century physician Rhazes. Pollen was identified as the cause in 1859 by Charles Blackley. In 1906, the mechanism was determined by Clemens von Pirquet. The link with hay came about due to an early (and incorrect) theory that the symptoms were brought about by the smell of new hay.

The conjunctiva provides lining for the inside of the eyelid as well as a coating for the sclera, the white portion of the eyeball. It typically serves to provide lubrication for the eye through the production of mucus and tears. When infected with AHC, patients will experience painful, red eyes, swelling of the conjunctival tissue, and frequent mucus discharge from the eyes accompanied by excessive tearing and subconjunctival hemorrhaging. This hemorrhaging is caused by the rupture of blood vessels beneath the conjunctiva giving the eyes a bright red appearance. Some patients also experience blurry vision and fever in addition to the common symptoms and one in every ten thousand cases exhibits paralysis similar to that of polio.

Diagnosis of subacute bacterial endocarditis can be done by collecting three blood culture specimens over a 24-hour period for analysis, also it can usually be indicated by the existence of:

- Osler's nodes

- Roth's spots

- Nail clubbing

Equine recurrent uveitis (ERU), also known as moon blindness, recurrent iridocyclitis or periodic ophthalmia, is an acute, nongranulomatous inflammation of the uveal tract of the eye, occurring commonly in horses of all breeds, worldwide. The causative factor is not known, but several pathogeneses have been suggested. It is the most common cause of blindness in horses. In some breeds, a genetic factor may be involved.

Blepharitis ( ) is one of the most common ocular conditions characterized by inflammation, scaling, reddening, and crusting of the eyelid. This condition may also cause burning, itching, or a grainy sensation when introducing foreign objects or substances to the eye. Although blepharitis is not sight-threatening, it can lead to permanent alterations of the eyelid margin. The overall etiology is a result of bacteria and inflammation from congested meibomian oil glands at the base of each eyelash. Other conditions may give rise to blepharitis, whether they be infectious or noninfectious, including, but not limited to, bacterial infections or allergies.

Different variations of blepharitis can be classified as seborrheic, staphylococcal, mixed, posterior or meibomitis, or parasitic. In a survey of US ophthalmologists and optometrists, 37% to 47% of patients seen by those surveyed had signs of blepharitis, which can affect all ages and ethnic groups. One single-center study of 90 patients with chronic blepharitis found that the average age of patients was 50 years old.

A positive BPF diagnosis includes the clinical symptoms (mainly the fever, purpuric lesions, and rapid progression of the disease), isolation of "Haemophilus Influenzae" Biogroup aegyptius from blood, and negative laboratory tests for "Neisseria meningitidis".

The negative tests for "Neisseria meningitidis" rules out the possibility of the symptoms being caused by meningitis, since the clinical presentations of the two diseases are similar.

Primary infection most commonly manifests as blepharoconjunctivitis i.e. infection of lids and conjunctiva that heals without scarring. Lid vesicles and conjunctivitis are seen in primary infection. Corneal involvement is rarely seen in primary infection.

Chronic bacterial prostatitis is a relatively rare condition that usually presents with an intermittent UTI-type picture. It is defined as recurrent urinary tract infections in men originating from a chronic infection in the prostate. Symptoms may be completely absent until there is also bladder infection, and the most troublesome problem is usually recurrent cystitis.

Chronic bacterial prostatitis occurs in less than 5% of patients with prostate-related non-BPH lower urinary tract symptoms (LUTS).

Dr. Weidner, Professor of Medicine, Department of Urology, University of Gießen, has stated: "In studies of 656 men, we seldom found chronic bacterial prostatitis. It is truly a rare disease. Most of those were E-coli."

A URI may be classified by the area inflamed.

Rhinitis affects the nasal mucosa, while rhinosinusitis or sinusitis affects the nose and paranasal sinuses, including frontal, ethmoid, maxillary, and sphenoid sinuses. Nasopharyngitis (rhinopharyngitis or the common cold) affects the nares, pharynx, hypopharynx, uvula, and tonsils generally. Without involving the nose, pharyngitis inflames the pharynx, hypopharynx, uvula, and tonsils. Similarly, epiglottitis (supraglottitis) inflames the superior portion of the larynx and supraglottic area; laryngitis is in the larynx; laryngotracheitis is in the larynx, trachea, and subglottic area; and tracheitis is in the trachea and subglottic area.

This classic herpetic lesion consists of a linear branching corneal ulcer (dendritic ulcer). During eye exam the defect is examined after staining with fluorescein dye. The underlying cornea has minimal inflammation.

Patients with epithelial keratitis complain of foreign-body sensation, light sensitivity, redness and blurred vision.

Focal or diffuse reduction in corneal sensation develops following recurrent epithelial keratitis.

In immune deficient patients or with the use of corticosteroids the ulcer may become large and in these cases it is called geographic ulcer.