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Singeing of hair

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singeing of hair medical significance inhalation injury burns

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Singeing of Hair

Definition

Singeing of hair refers to the superficial burning, scorching, or charring of hair by dry heat, flames, or hot gases - without necessarily destroying the underlying skin. The affected hair becomes curled, twisted, blackened, brittle, and may break off or be totally destroyed.

Medicolegal / Forensic Significance

Singeing of hair is an important physical sign in forensic medicine and has several key implications:

1. Differentiating Burn Types

Hair singeing helps identify the nature and cause of thermal injury:
CauseSingeing of Hair
Flame burnsAlways present; hair curled, twisted, blackened
Hot solid body / molten metalPresent; hair singed and distorted
Kerosene / petrol burnsPresent with sooty blackening and characteristic odour
Scalds (hot liquids)Absent - a key distinguishing feature
Corrosive substancesAbsent - no line of redness or singeing
Electrical burnsUsually absent (entry/exit marks characteristic instead)
  • The Essentials of Forensic Medicine and Toxicology, 36th ed., p. Burns section
Burns produced by flame may or may not produce vesication, but singeing of the hair and blackening of the skin are always present - this is a classic forensic teaching point.

2. Close / Contact Firearm Injuries

Singeing of the hair around a gunshot wound entry site indicates a close or contact range discharge. When the gun is fired at close range, hot gases, flames, and powder escape from the muzzle along with the bullet and produce singeing of the surrounding hair. This is valuable for estimating the range of fire.
  • The Essentials of Forensic Medicine and Toxicology, 36th ed., p. Firearms section
  • P.C. Dikshit Textbook of Forensic Medicine and Toxicology, Medicolegal Importance of Hair

3. Establishing Ante-mortem vs. Post-mortem Burns

In the post-mortem examination, the external findings including burns, scalds, and singeing of the hair must be systematically documented - they help establish whether injuries occurred before or after death.
  • Parikh's Textbook of Medical Jurisprudence, External Examination

Clinical Significance (Inhalation Injury)

In clinical/surgical medicine, singeing of nasal and facial hair is a key warning sign of respiratory tract burns and inhalation injury:
Warning signs of burns to the respiratory system include:
  • Burns around the face and neck, blistering inside the mouth
  • History of being trapped in an enclosed space
  • Change to / hoarseness of voice
  • Stridor
  • Singeing of facial and nasal hair - indicates exposure to flame or superheated gases close to the airway
  • Bailey and Love's Short Practice of Surgery, 28th ed., Summary Box 46.4
Singed nasal hairs alongside carbonaceous sputum are two of the most easily recognized signs of significant smoke inhalation injury, and their presence should prompt immediate airway assessment and consideration of early elective intubation before progressive oedema causes obstruction.

Microscopic Appearance of Singed Hair

On microscopic examination, hair subjected to heat shows:
  • Cuticle blackened, dry, shrivelled
  • Hair shaft curled and twisted
  • Cortical cells elongated and flattened, deeply stained
  • Small haemorrhages in deeper layers
  • Vacuoles present

Summary

Singeing of hair is significant in two main contexts:
  1. Forensic medicine: Confirms flame/heat as the cause of burns; distinguishes from scalds or chemical burns; indicates close-range firearm discharge; important in post-mortem documentation.
  2. Clinical medicine: Singed nasal/facial hair is a red-flag sign of upper airway thermal injury, mandating urgent airway assessment.
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