Irritability is an excessive response to stimuli.

The term "irritability" is used for infants and young children who, when ill, are especially fussy, whiny, and fretful, despite attempts at comforting and soothing them.

Parents are usually very aware of their child's normal behavior and may pick up early changes that the health care provider wouldn't notice. This can help diagnose illness early.

Irritability can be a very early sign of serious problems. Although irritability is not a symptom of any specific illness, it should arouse suspicion in the parent that something might be wrong with the child, even though there may not yet be other symptoms.

Causes of irritability include:

• Alcohol or drug withdrawal state
• Autism spectrum disorders
• Cancer
• Colic in infants
• Congenital infections
• Diabetes or other metabolic disease
• Drug reaction
• Ear infection
• Encephalitis
• Fracture, sprain, or other bone, joint, or tissue injury
• Headache (migraine or other)
• Head trauma
• Hydrocephalus
• Hypoglycemia
• Intestinal obstruction
• Intracranial bleeding or abscess
• Iron deficiency anemia
• Lead poisoning
• Meningitis or other serious infection
• Milk intolerance
• Nutritional deficiencies
• Pinworm
• Psychiatric illnesses
• Sleep disorders
• Tay-Sachs or other genetic disease
• Teething
• Viral infection