Common Side Effects of Flea, Tick & Worm Treatments in NZ: What to Watch For
Why this matters
Most pets do well on parasite treatments. Mild, short-lived effects can happen, especially with a new product. Know what is normal, how to dose safely, and when to seek help.
After a chew: what you might see
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Mild tummy upset such as soft stools or a single vomit.
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Brief lethargy or a smaller appetite for one meal.
These usually pass within a day. Offer water and a quiet place to rest. If vomiting repeats or your pet seems unwell, call your vet.
After a spot-on: what you might see
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Damp fur or a small clump at the application site.
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Mild skin irritation or increased grooming.
Keep other pets and children away from the site until dry. If redness or itch persists beyond a day, contact your vet.
If a cat tastes the product
Some cats drool or paw at the mouth if they groom the area. Offer water, monitor, and next time apply at the back of the head where they cannot reach. If signs persist, speak with your vet.
Rare but serious signs
Seek urgent veterinary care if you see wobbliness, tremors, seizures, breathing changes, repeated vomiting, facial swelling, or extreme lethargy. Stop using the product until your vet advises a plan.
Simple ways to reduce tummy upset with chews
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Give with or soon after a meal.
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Avoid new treats or rich foods on dose day.
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Dose at a calm time and keep your schedule consistent.
Trusted options in our NZ range
Use as directed on the label and match the correct weight band every time.
When to call your vet
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Side effects last longer than 24 hours.
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Your pet has a medical condition or takes other medicines.
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You are unsure about redosing after a vomited dose.
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Your pet shows any weakness, wobbliness or breathing changes.
Safe use checklist
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Weigh your pet and choose the correct pack each time.
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Use dog products on dogs only. Never use dog products on cats.
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Do not split doses between pets.
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Apply spot-ons to clean, dry skin and keep the site away from children and other pets until dry.
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Read the label before every dose.
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If your pet is pregnant, lactating, very young, senior, or unwell, ask your vet first.
FAQ
Are side effects common
Most are mild and short lived. Serious reactions are uncommon, but monitor your pet after any new product.
My dog vomited after a chew. Should I give another
Do not redose without advice. Timing rules vary by product. Ask your vet to confirm next steps.
Can I switch to a different application
Yes. Some pets do better with a chew, others with a spot-on. Start the new product when the previous one would have been due.
Do indoor cats still need prevention
Often yes. Fleas can thrive in warm homes. A simple, on-time plan helps prevent flare ups.
Need help choosing
Tell us your pet’s age, weight and routine and we will suggest a simple plan for your home. Contact us.
