Carbolic acid is also known as phenol.

In pure form, it looks like a short prismatic, needle-like crystal that has a sweet burning taste.

They are hygroscopic in nature which turns pink and liquefies when exposed to air. It has a characteristic carbolic or phenolic smell. It is slightly soluble in water and can completely solubilize in glycerine, ether, alcohol, and benzene.

The commercial carbolic acid is sold as a dark brown liquid containing numerous impurities or mixture chiefly cresol.

Where is Carbolic Acid Found?

Carbolic acid can be found in:

• Adhesive dyes
• Lubricating oils
• Perfumes
• Textiles
• Various antiseptics
• Various disinfectants
• Various germicides
• Other products may also contain carbolic acid

Route of Exposure

Route of exposure could be either by direct ingestion or by contact. Inside the body, this phenol is converted into hydroquinone and pyrocatechol. Its fatal dose is 1 to 2 grams and its fatal period is considered as about 3 to 4 hours. The poisoning by carbolic acid is known as Carbolism. 

Mechanism of Action

1. Local Effects

a. Skin

• It caused burning and numbness due to damage to nerve endings.  Superficial burn is pale grey but deep burns are black in color.
• It precipitates protein and coagulates cell components
• Produces white opaque eschar which is painless and falls off in a few days by leaving a brown stain on the skin
• There may be Necrosis and gangrene of the tissue, which becomes green white, or brown white. The dead tissue slough readily.

b. Digestive Track

• Hot burning pain extends from mouth to stomach followed by tingling and later anesthesia.
• (swallowing) and speech may become painful.  The lips, mouth, and tongue are corroded which soon become white and hardened.
• Nausea and vomiting are also seen in about 20 % of cases of carbolic acid poisoning.
• Respiratory tract.
• Pulmonary and laryngeal oedema developed due to irritation.
• Breathing becomes slow and labored which may progress to respiratory failure.
• The poison may enter into the lungs while vomiting and consequently causing v=bronchitis and bronchopneumonia.

2. Systemic Effects

• Phenol is a depressant of the nervous system specially for the respiratory center.
• It causes Headache, giddiness, tinnitus, muscular spasm, and later collapse, unconsciousness and coma occur.
• Pupils become contracted.
• Breathing is torturous. The pulse rate is increased. The face becomes cold and cyanosed
• Convulsions and locking of the jaw occur.
• Marasmus is seen in chronic phenol poisoning.
• Urine is scanty, and contains albumin and free hemoglobin; suppression may follow.
• Carboluria: in the body phenol is partially oxidized into hydroquinone and pyrocatechol and is excreted in the urine along with unchanged phenol. The further oxidation of hydroquinone and pyrocatechol in urine is the cause of green coloration. This is known as Carboluria.
• Hydroquinone and Pyrocatechol may cause pigmentation in the cornea and various cartilages and this condition is called ad Ochronosis

Cause of Death due to Carbolic Acid Toxicity

1. Syncope
2. Asphyxia due to Failure of respiration
3. Oedema of glottis 
4. Complication e.g. Bronchopneumonia

Treatment

An emetics may often fail in such cases due to the anesthetic effect

1. The stomach should be washed with plenty of lukewarm water containing animal charcoal, olive oil, castor oil, magnesium or sodium sulfate, or saccharated lime with which phenol combines and forms harmless products.
2. Soap solution or 10 % glycerine may also be used and washing of the stomach should be continued until the washout liquid appears clear and colowebsiteess.
3. When lavage is completely done, Magnesium sulfate or medicinal liquid paraffin should be left in the stomach.
4. Saline containing 7g of sodium bicarbonate/liter should be given to combat circulatory depression, dilute carbolic acid content in blood, and encourage excretion by producing diuresis.
5. In case of renal failure in such cases, hemodialysis should be performed
6. If carbolic acid accidentally falls into the body, the contaminated clothing should be immediately removed and the skin should be cleaned with soap and water.

Post-Mortem Appearance

1. The stomach mucosal folds are swollen and converted by opaque, coagulated, grey, or brown mucous membrane. The mucous membrane is thickening and gives a white leathery appearance.
2. Liver and spleen show whitish hardened patch
3. Kidney shows hemorrhagic nephritis, Phenol causes PCT Necrosis

Key Points

• Phenol delays putrefaction
• It causes PCT Necrosis
• It causes a leathery appearance of the Stomach mucosal wall
• Carbolic acid in urine can be confirmed using Benedict/Fehling’s solution, ferric chloride, and bromine water

Conclusion

This article is solely for educational purposes. It should not be used to treat or manage an actual poisoning. If you or someone you're with has been exposed to carbolic acid toxicant, call or go to the nearest hospital for immediate help.