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This calculator provides general guidance only. Zyrtec dosing is based on age, not weight. Always read product labels and consult a healthcare provider for children under 2 or those with medical conditions.
Calculate the appropriate cetirizine dose for your child based on age
Weight is for reference only - Zyrtec is dosed by age
| Age | Dose (mg) | Liquid (1mg/mL) | Chewables (5mg) | Frequency |
|---|---|---|---|---|
| Under 2 years | Ask Doctor - Not Recommended | |||
| 2-5 years | 2.5 mg | 2.5 mL | ½ tablet | Once daily |
| 2-5 years (max) | 5 mg | 5 mL | 1 tablet | Once daily or 2.5mg BID |
| 6-11 years | 5-10 mg | 5-10 mL | 1-2 tablets | Once daily |
| 12+ years | 10 mg | 10 mL | 2 tablets | Once daily |
BID = twice daily. Some liquid formulations are 5mg/5mL - always check your product label.
| Zyrtec (Cetirizine) | Claritin (Loratadine) | Benadryl (Diphenhydramine) | |
|---|---|---|---|
| Minimum Age | 2 years | 2 years | 2 years (varies) |
| How Often | Once daily | Once daily | Every 4-6 hours |
| Duration | 24 hours | 24 hours | 4-6 hours |
| Drowsiness | Some (less than Benadryl) | Least likely | Most likely |
| Speed of Action | 1 hour | 1-3 hours | 15-30 minutes |
| Best For | Daily allergies | Daily allergies | Acute reactions, hives |
Common:
Less Common:
Yes, Zyrtec (cetirizine) is designed for daily use and is safe for long-term daily administration in children 2 years and older. Unlike Benadryl, it's a 'second-generation' antihistamine made for ongoing allergy control.
Zyrtec can be given any time of day. Since it can cause drowsiness in some children, many parents give it at bedtime. Others prefer morning so it's at peak effect during the day when allergies are worst. The key is giving it at the same time daily.
Unlike pain medications, antihistamine absorption and metabolism are fairly consistent across different body weights within age groups. The FDA-approved dosing is based on age because clinical trials were designed this way. However, very underweight or overweight children may need dose adjustments.
Yes, Zyrtec can safely be given with acetaminophen (Tylenol) or ibuprofen (Motrin) as they work on different systems. However, don't give Zyrtec with other antihistamines (like Benadryl) as this doubles the antihistamine effect and increases side effects.
Some children experience a 'paradoxical reaction' to antihistamines, becoming more active rather than drowsy. This is more common in young children. If this happens and is bothersome, talk to your doctor about trying a different antihistamine like loratadine (Claritin).
Zyrtec may help with mild symptoms like hives or itching from food allergies, but it does NOT prevent or treat anaphylaxis (severe allergic reactions). If your child has food allergies, epinephrine (EpiPen) is the first-line treatment for reactions. Always carry prescribed epinephrine.
Zyrtec typically starts working within 1 hour, with peak effect at 4-8 hours. It lasts 24 hours. For best results with seasonal allergies, start taking it daily 1-2 weeks before allergy season begins.