Bleach refers to a large class of compounds used to whiten or color-lighten materials. They are frequently used for cleaning and disinfection; bleaches kill or control most types of viruses, bacteria, molds, mildews, and algae. Other, less documented, uses include weed killing and preservation of cut flowers. As such, bleaches are ubiquitous. 
Bleach is chlorine-based such as calcium hypochlorite (bleaching powder) and non-chlorine (peroxidase-based).
Bleaching action occurs through oxidation or reduction. Chlorine bleaches work through oxidation; they break the chemical bond of the chromophore (a color-producing portion of pigment) rendering it non-reactive with light. Reductions convert double bonds to single bonds, again making them non-reactive to visible light.
An additional interesting and useful property of bleaches relates to their antimicrobial (disinfecting) properties. Winter et al. observed that bleaches disinfect by denaturing (unfolding) bacterial proteins, causing them to clump and become useless. This is the same reaction as cooking an egg; in the same fashion, an egg cannot be uncooked.
Bleach, as subsequently used here, refers to common household bleach sold under such brand names as Clorox et al. Bleach contains 3% to 8 % sodium hypochlorite (NaOCl); sodium hydroxide (NaOH) is added to slow decomposition. There are industrial and concentrated forms of bleach that are used to clean equipment and treat water supplies, which are not covered here. For concerns and exposures, see the individual exposure MSDS (Material Safety Data Sheet.) 
Additionally, you must be aware of the many uses for bleach and realize that people may combine chemicals to achieve an initially desirable goal (fumigation, foliage control, area cleaning, etc.). These chemical combinations may yield undesirable products of the reaction.
Causes of bleach exposure include:
Bleach is a common household item used for surface cleaning and disinfection, cleaning clothes, and treating fabric. Household bleach, used according to label directions, including recommended ventilation and protection, is surprisingly non-toxic to humans. This may lead to complacency. Misapplied, especially when mixed with other substances, it can be harmful or even lethal.
McKenzie et al. reported in a 2010 pediatric study over a 16-year period that just under 270,000 US children (< 5 years of age) were injured by household cleaning products. Bleach was the leading source (37%) and usually by ingestion (63%). A spray bottle was the most common source (40%).
Bleach is a corrosive, especially to metal surfaces. Bleach itself is readily diluted with water and can be neutralized on surfaces, including skin, with sodium thiosulfate (if necessary).
Direct reaction: Bleach reacts with biological tissues, causing irritation and cell death by protein denaturation. This reaction is most severe for the more sensitive tissues such as the respiratory system and eyes and less severe for more resistant tissues such as GI tract (which is accustomed to low pH) and skin (which is adapted to be in contact with the environment).
Indirect reaction: A high index of suspicion must be maintained for secondary exposures from intentional or unintentional mixing with other chemicals. These secondary reactions may cause the production of more toxic chemicals, each having its toxicity profile. Chief among these is chlorine gas, which has been used as a chemical warfare agent.
The toxicity of bleach depends on where it is applied. It causes significant eye irritation and irritates the mouth and throat but is fairly benign when ingested.
A dangerous problem with bleach occurs if bleach is mixed with other household cleaners, especially toilet bowl cleaners and ammonia. These mixtures result in the release of chlorine gas, an asphyxiant. When chlorine gas contacts moist tissues, such as eyes or lungs, hydrochloric acid (HCl) results. This acid is a digestive molecule and damages tissue. It will cause damage to the airways, asphyxiation, and can result in death.
A routine history and physical exam are sufficient. Be sure to get the container, even if you have to send the family back home for it.
If the bleach was mixed with another chemical, especially toilet bowl cleaners or ammonia, see the section on chlorine gas inhalation.
Eyes: At home, flush with tap water. In the Emergency Department, use a topical anesthetic and irrigate with a balanced salt solution. Control pain with a topical anesthetic, such as tetracaine or proparacaine. Place two drops on the medial canthus of the eye then gently pry open the lid. Direct installation is nearly impossible due to blepharospasm. The cornea should be stained with fluorescein and examined under a slit lamp. Look for corneal ulcers or other signs of damage. Corneal abrasions will be common, either from the patient rubbing his eyes or the home treatment to irrigate. Corneal edema may also be evident. A Wood's lamp may substitute for a slot lamp, but significant detail will be lost. Irrigate copiously and be sure to check pH. Advice from an ophthalmologist or emergency physician is in order. 
Skin: At home, wash with gentle soap and water. Treatment is the same in the Emergency Department.
Mouth/throat: In the home and Emergency Department, give plenty of water to drink. Milk may be more soothing but not necessarily.
Stomach/GI tract: At home and in the Emergency Department, do not induce vomiting; if the bleached burned on the way down, it would burn on the way back up. Give plenty of water.
Respiratory: Use albuterol MDI for signs of bronchospasm; asthmatics may require more aggressive treatment. If exposed to chlorine gas from mixing chemicals, a much more severe course is expected. Bronchoscopy may be required, with lavage as indicated. Admission for observation may be needed as the severity of injury may not be immediately apparent.
Common household bleach is relatively benign to the skin and GI tract; dilution is usually sufficient.
Eye exposure requires symptomatic treatment; see chemical conjunctivitis.
Respiratory exposure requires symptomatic treatment with special attention to those with reactive airway disease.
The relative lack of toxicity of ingested bleach belies the toxicity of bleach mixed with other household chemicals.
Bleach toxicity can be serious, and in most cases, it is a preventable injury. While the physicians play a role in the treatment of the injury, the nurse and pharmacist should educate the patient on prevention. The public should be educated on proper labeling and storage of all hazardous chemicals in the home. In addition, the chemicals in the home should not be mixed. When using bleach around the home, one should wear safety goggles, gloves, and long-sleeved garments. Pets and children should be kept away from the treated site for at least 8-12 hours. In addition, when using bleach indoors, adequate ventilation is necessary. The pharmacist should educate the public on symptoms of bleach toxicity and when to seek medical assistance. Finally, patients with lung disease should refrain from using bleach in the home as the fumes may aggravate the disease and lead to an acute breathing crisis. (Level V)
The majority of people exposed to bleach do recover without residual sequelae. However, those with pre-existing lung disease may suffer from lung impairment if the fumes are inhaled. The skin irritation is usually relieved quickly as long as the site is thoroughly irrigated with water. In patients with reactive airway disease, coughing and sloughing of the mucosa may persist for a few days. Long-term follow up reveals that some of these patients may have residual lung and vision impairment for up to 2-3 years after the acute exposure. (level V)