What would cause excessive sweating in a toddler i.e. meaning with no known reason such as heat or running and playing etc?

Excessive sweating in toddlers without an obvious cause such as heat or physical activity can be a sign of underlying medical conditions. Several possible causes include:

Hyperthyroidism: An overactive thyroid gland can cause an increase in metabolism and body temperature, leading to excessive sweating. Symptoms of hyperthyroidism in toddlers may include weight loss, increased appetite, irritability, diarrhea, and rapid heart rate.

Medications: Certain medications, such as certain antibiotics and antihistamines, can cause excessive sweating as a side effect.

Infection: Some infections, such as viral infections and urinary tract infections, can cause a fever and excessive sweating. Symptoms of an infection may include fever, chills, body aches, loss of appetite, and fatigue.

Anxiety or Stress: In rare cases, excessive sweating in toddlers may be related to anxiety or stress. This may be more common in toddlers who are going through a new or stressful situation, such as starting daycare or transitioning to a new bed.

Genetic Conditions: Some genetic conditions, such as cystic fibrosis and Prader-Willi syndrome, can cause excessive sweating.

It's important to consult a pediatrician to determine the cause of excessive sweating in a toddler. The doctor can perform a physical exam, order laboratory tests, and make any necessary referrals to specialists for further evaluation and treatment.