Chicken Pox (Varicella) in Babies and Toddlers
The short answer
Chicken pox (varicella) is a highly contagious viral infection that causes an itchy rash of small, fluid-filled blisters. Thanks to the varicella vaccine, it is much less common than in previous decades, but it can still occur in unvaccinated children or as a mild breakthrough case in vaccinated children. The rash typically appears in waves over 3-5 days, with bumps progressing from red spots to blisters to scabs. Most children recover fully at home within 1-2 weeks.
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By Age
What to expect by age
0-6 months
Babies under 6 months are partially protected by maternal antibodies if the mother had chicken pox or was vaccinated. However, chicken pox in very young infants can be more serious. Neonatal varicella (if the mother develops chicken pox around the time of delivery) is a medical emergency. If a young baby is exposed to chicken pox, contact your pediatrician promptly as preventive treatment may be available.
6-12 months
Babies between 6 and 12 months have lost most maternal antibodies but are not yet old enough for the first dose of varicella vaccine (given at 12 months). This makes them vulnerable if exposed. If your baby develops chicken pox at this age, the rash typically starts on the trunk, face, and scalp and spreads outward. Oatmeal baths, calamine lotion, and keeping nails short can help manage itching. Do not give aspirin to children with chicken pox due to the risk of Reye syndrome.
1-3 years
The first dose of varicella vaccine is given at 12-15 months. Vaccinated children can still get a mild case called "breakthrough varicella," which typically involves fewer than 50 lesions and milder symptoms. Unvaccinated toddlers tend to have more severe cases with 200-500 blisters. The rash appears in "crops" over several days, so you will see bumps at different stages (spots, blisters, and scabs) all at once. Children are contagious from 1-2 days before the rash until all blisters have crusted over.
What Should You Do?
When to take action
- A rash that starts as small red bumps, becomes fluid-filled blisters, and then crusts over
- New crops of blisters appearing for 3-5 days while older ones are healing
- Low-grade fever, mild headache, and decreased appetite for the first few days
- Itchiness that peaks when blisters are forming and improves as they scab
- A milder case with fewer blisters in a vaccinated child
- Your baby has been exposed to chicken pox and is under 12 months or unvaccinated
- The rash is very widespread with many blisters, especially in an unvaccinated child
- Your child has been itching severely and you need guidance on comfort measures
- You are unsure whether your child's rash is chicken pox or something else
- Your baby is under 4 weeks old and has been exposed to or develops chicken pox
- Blisters become very red, swollen, warm, or produce pus, indicating bacterial superinfection
- Your child develops a high fever (over 104F / 40C), especially one that returns after initially improving
- Your child seems very ill, confused, has a stiff neck, or has difficulty walking
- Your child has a weakened immune system and develops chicken pox
- Your child develops difficulty breathing or a persistent cough during chicken pox
Sources
Related Resources
Trust your instincts. If something feels wrong, reach out to your pediatrician.
Worrying about your baby means you care. That is a good thing.
Related Medical Concerns
My Baby Has a Fever and a Rash
The combination of fever and rash in a baby is very common and is usually caused by a viral infection such as roseola, hand-foot-and-mouth disease, or other viral exanthems. A rash that appears after a fever breaks (as in roseola) is typically benign. However, certain fever-rash combinations, particularly non-blanching purple spots (petechiae or purpura), require immediate medical attention.
Baby Hives (Urticaria)
Hives are raised, red, itchy welts that can appear suddenly on your baby's skin. They are most often caused by a viral infection or an allergic reaction to food, medication, or an insect bite. While they can look alarming, hives are usually harmless and resolve on their own, though any breathing difficulty needs immediate emergency care.
Blisters on Baby's Skin - Causes and When to Worry
Blisters on a baby's skin can have many causes ranging from harmless (sucking blisters, friction blisters) to conditions requiring medical attention (burns, infections like hand-foot-and-mouth disease, impetigo, or herpes). A single blister on a newborn's lip or hand from sucking is very common and harmless. Multiple blisters, blisters with fever, blisters that spread rapidly, or blisters in a newborn under 1 month should be evaluated by a doctor.
My Baby Has a Viral Rash
Viral rashes are extremely common in babies and young children and appear as widespread pink or red spots, often during or after a viral illness like a cold. They are caused by the body's immune response to the virus, not by anything contagious on the skin itself. Most viral rashes are harmless and fade on their own within a few days without any treatment.
My Baby's Head Shape Looks Abnormal
Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.
Achondroplasia (Dwarfism) in Babies
Achondroplasia is the most common form of short-limbed dwarfism, affecting about 1 in 15,000 to 40,000 births. It is caused by a mutation in the FGFR3 gene and is usually apparent at birth with characteristic features including short limbs, a larger head, and a prominent forehead. Intelligence is normal. With monitoring for specific complications and supportive care, children with achondroplasia lead full, active, and independent lives.