Stages of a chemical injury

What happens during a chemical injury?

Stages of development of a chemical injury/lesion. 

The mechanism of development of the lesion may be divided into three phases:

  • Contact between the chemical product and the tissue.
  • Penetration of the chemical product into the tissue.
  • Reaction between the product and the biological component of the tissue.

Skin or eye contact occurs when the chemical product is splashed on the skin or in the eye. Contact with the digestive tract ( mouth, oesophagus, stomach) occurs when the chemical product is swallowed. In the case of the airways, it takes place when vapours of the chemical product are inhaled.

Once the product is in contact with the tissue, it may penetrate the tissue, in spite of the biological barriers. The characteristics of the chemical product define its penetration potential and penetration rate into tissue.


  • A solid chemical product cannot readily penetrate through the skin.
  • A small chemical molecule generally penetrates more quickly than a large molecule.
  • A molecule penetrates more readily if it is lipophilic.

The chemical product will penetrate into tissue until it encounters a biological constituent with which it can react. The penetration depth of the chemical product into the tissue before it reacts therefore depends on its type.

The chemical product is subsequently able to react with its biological target. 

Once the chemical product has reached the biological constituent of the target tissue, the chemical reaction takes place. The biological equilibrium is changed, the tissue is locally destroyed and the lesion forms.

The lesion therefore only develops during the chemical reaction, once the chemical product has reached its target. Each splash of chemical product contains a very large number of molecules capable of reacting with a target molecule or with a target cell of the human body.

The lesion progresses in this manner for as long as any chemical product still remains in contact with the tissue and has not yet reacted.

Rapid intervention following contact makes it possible to restrict the extent of the lesion:

Emergency decontamination is paramount.

Factors that worsen the lesion. 

The type, depth and severity of the lesion depend on many factors:

  • The nature of the aggressive chemical product.
  • Its concentration.
  • The contact time between the tissue and the chemical product.
  • The temperature of the chemical product and the pressure.