Wasp sting swelling: when is it dangerous?
By Wespenprofis.ch · Reviewed by:Fachbewilligung Schädlingsbekämpfung VFB-S · Updated: 3 July 2026
At a glance
Redness and swelling of a few centimetres around the puncture site is a normal reaction and usually subsides within a few days. It becomes dangerous if the swelling spreads considerably, affects the throat, or is accompanied by symptoms such as breathing difficulties, hives all over the body or dizziness. In that case, call the emergency number 144 immediately.
This article is not a substitute for medical advice. If you experience difficulty breathing or swelling around the throat, call 144 immediately.
Almost every wasp sting swells up — that is a normal reaction of the immune system. What matters is being able to tell a harmless local swelling from the signs of a more serious reaction. This article is not a substitute for medical advice.
Normal local swelling
Redness, warmth, itching and swelling of a few centimetres around the puncture site are part of the usual reaction to insect venom. It occurs because the body reacts to the proteins contained in the venom, and it generally subsides on its own within two to three days. Cooling noticeably eases the discomfort; you will find guidance on this in our article «Treating a wasp sting».
When the swelling gets larger
Some people develop what is known as a large local reaction: the swelling spreads beyond the immediate puncture site, for example across the entire forearm, or around an eye if the sting was to the face. It may also peak after two to three days and measure well over ten centimetres. This is unpleasant, but usually harmless as well, as long as no other symptoms appear. Anyone who repeatedly develops severe large local reactions should discuss this with a doctor, as it can point to an increased risk of allergy. You can read more in our article «Recognising an insect venom allergy».
Warning signs that require medical assessment
Seek medical advice promptly if the swelling continues to spread over several days instead of subsiding, if the skin feels very hot or painful, or if a fever develops — these can be signs of an infection. You will find details in our article «Infected wasp sting — what to do?».
Emergency: swelling in the throat or a generalised reaction
Swelling in the mouth, throat or pharynx is always an emergency, as it can narrow the airways. The same applies if breathing difficulties, hives all over the body, dizziness or circulatory collapse also occur. In these cases, call the emergency number 144 (the Swiss ambulance service) immediately. You will find the basics on what to do after a sting in our pillar article «Wasp sting — what to do?».
Frequently asked questions
At what size is swelling no longer normal?
Local swelling of a few centimetres around the puncture site is normal. If it keeps growing noticeably over several days, extends across an entire body region such as the whole wrist, or affects the throat, it should be assessed by a doctor.
How long may swelling after a wasp sting last?
It usually goes down on its own within two to three days. If it persists for longer or increases instead of subsiding, a medical assessment is advisable.
What is a "large local reaction" to an insect sting?
A large local reaction is local swelling that extends well beyond the puncture site, for example affecting the whole forearm. It is usually harmless, but if it happens repeatedly it should be discussed with a doctor.