Exploring the Causes of Body Aches When You’re Sick: What You Need to Know

Body aches when sick occur because your immune system releases chemicals that cause inflammation and muscle pain.

Why

When you fight infection, immune cells release cytokines and prostaglandins. These cause inflammation, fever and muscle and joint aches.

Common in

Flu, COVID-19, colds, strep throat and mono.

What helps

• Rest and fluids.
• Ibuprofen or acetaminophen.
• Warm bath.

Duration

Aches often fade in 3 to 5 days.

See a doctor

If you have severe aches, high fever, stiff neck or symptoms over 10 days.

Cytokine mechanism

Body aches during infection come from the immune response. Cells release cytokines such as interleukin-1, interleukin-6 and tumor necrosis factor that raise prostaglandin E2, which increases pain sensitivity and fever. Muscles and joints become tender, and the brain triggers a sickness behavior of rest.

• Influenza typically causes more severe aches than the common cold, and symptoms start abruptly.
• Fever raises body temperature by 1 to 4 degrees C as part of defenses.
• COVID-19, dengue, strep and mononucleosis also cause body aches.

Care and duration

Rest, fluids, and acetaminophen or ibuprofen (not aspirin for children and teens) reduce aches. Aches typically fade within 3 to 7 days as fever drops. Seek care for aches with stiff neck, rash, difficulty breathing, confusion, fever over 39.4 C (103 F) or lasting over 3 days. Antivirals such as oseltamivir work best when started within 48 hours of flu symptoms in high-risk people.

Cytokine mechanism

When the immune system fights infection, it releases cytokines such as interleukin 1, interleukin 6 and tumor necrosis factor. These signal the brain to raise body temperature and produce prostaglandins, causing muscle aches, fatigue and fever. This is part of sickness behavior.

Care and duration

Rest, fluids and pain relievers as directed. Flu aches last several days. See a doctor for severe symptoms, trouble breathing, confusion or persistent fever.

Why muscles ache with infection

During infection, prostaglandins and cytokines such as IL-1 beta and TNF alpha act on the hypothalamus and sensitize pain nerves in muscles. Flu causes myalgia in about 50 percent of cases. COVID-19 causes myalgia in 15 to 40 percent. The aches usually peak on days 2 to 3.

Management

Use acetaminophen or ibuprofen as directed, fluids, rest and a warm bath. Do not give aspirin to children. Seek medical help for muscle pain with dark urine (rhabdomyolysis), severe weakness, stiff neck, trouble breathing, fever over 103 F or symptoms over 10 days. Antivirals like oseltamivir work best within 48 hours of flu onset.

Based on data from the CDC and the NIH