The bite of a blackfly can cause severe pain and swelling – and in the worst cases, an allergic reaction or blood poisoning. Black flies look like tiny flies, but their bites are extremely painful and can cause severe swelling or bruising. The bites are especially dangerous if an allergic reaction or infection occurs. How do you treat a blackfly bite and what can you do to protect yourself from the bloodsucking parasites? Get answers to the 13 most important questions about black flies here.
What are black flies?
Black flies (Simuliidae) are two-winged insects that belong to the group of mosquitoes. About 2,000 species of black flies are distinguished, about 50 of which are found in Germany. Five of these subspecies are known to attack humans. Just like mosquitoes, the females of the blackfly need blood to lay eggs. Unlike many other biting insects, however, black flies are so-called “pool suckers”: they do not have a biting proboscis, but rather saw-like biting tools with which they scratch the skin of their host. If blood then collects in the tiny wound, they suck it out.
How do you recognize a blackfly bite?
Blackflies fly silently and are usually not noticeable on the skin, so you usually don’t notice them or notice them too late. However, the bite causes typical symptoms:
- Initially, only a small red spot can be seen where the blood pool has formed – sometimes blood still flows after.
- Then a wheal forms around the skin lesion and the skin is red.
- At first, the spot hurts, later it begins to itch. Both itching and pain usually turn out more violent than in normal mosquito bites.
- Sometimes a bruise develops.
- Small skin nodules, edema or purulent blisters may develop at the bite site. The redness and swelling can be up to ten centimeters in diameter.
How long it takes to heal from such a bite varies: at best, it occurs after a few days, but can also drag on for a period of several weeks.
What are the possible consequences of such a bite?
During the bite, the blackfly releases saliva into the wound, which contains a mixture of different substances with different effects. Although the exact effects have not yet been fully researched, the following effects of these substances are known so far:
- Localized inhibition of blood clotting and anesthesia of the nerves, to which the body reacts with the release of histamine and subsequent itching.
- Negative effect on the respiratory center
- Harmful effect on the heart and blood vessels
There is also the possibility of an allergic reaction to the toxic substances in the saliva of the mosquito, which it releases into the wound with the bite. With repeated blackfly bites, circulatory problems up to an allergic shock can be the result. In rare cases, the bite may also become infected as a result of contamination of the wound with germs. If the infection is not treated in time, blood poisoning may result in the worst case.
Do black flies transmit diseases?
In African countries and in Central and South America, the blackfly is considered a carrier of the so-called river blindness. In Germany, diseases are very rarely transmitted by their bite. Which pathogens can be transmitted by black flies has not yet been fully researched. For example, it has not yet been clarified whether black flies are possible carriers of Lyme disease.
Are blackfly bites dangerous?
Blackfly bites – actually, blackfly bites – are more painful than a normal mosquito bite and usually cause a more severe physical reaction. Nevertheless, they are normally no more dangerous than the bite of a snake. However, due to the comparatively larger wound that results from the insect bite, the risk of infection is higher. Moreover, relatively many people are allergic to the mosquito’s saliva and severe allergic reactions may occur. Therefore, individual doctors warn of the dangers of the bite of the blackfly – but health authorities currently see no cause for alarm.
Blackfly bite: what to do?
If you are bitten by a blackfly, it is generally recommended to immediately disinfect and cool the corresponding area. Suitable for this purpose are, for example, cold water, cooling gel or a cold pack – if nothing is at hand, a little of your own spit will do for the first moment. It is important not to scratch, so that the poison does not spread further in the body and no pathogens get into the wound. A plaster helps to protect the bite from irritation from the outside. A cooling ointment can be used to relieve itching. If necessary, the swelling can be treated with cortisone ointment or anti-allergic agents (antihistamine) from the pharmacy. Home remedies such as onions or lemons are rather unsuitable for treatment: Medical experts do not attribute any benefit to them – but presumably they do not do any harm either.
When is treatment by a doctor necessary?
If a blackfly bite shows no improvement or even worsens after one day, you should consult a doctor to be on the safe side. If a child is affected, or if an adult has received several bites, it is better to see a doctor right away. Also, if a red line forms on the skin, it is advisable to see a doctor: This may indicate inflammation of the lymphatic channels. In case of bacterial infection of the bite, treatment with antibiotic is necessary. Furthermore, you should consider symptoms such as fever, headache, dizziness or swelling of the lymph nodes as an alarm signal. If left untreated, such lymphadenitis can lead to dangerous blood poisoning. In case of severe swelling or the extensive formation of wheals and redness, an allergy may possibly be present and you should see a doctor as soon as possible. In the worst case, a life-threatening allergic shock can be the result.
What do black flies look like?
Measuring approximately two to six millimeters, black flies are smaller than mosquitoes. Their color is usually dark, but varies from black to gray to reddish-yellow. The insects resemble a fly with a small head, but appear squat and humped when viewed from the side. The fact that they look like small black flies is reflected in their English name: Black Fly. They are often confused with gnats, which are also pool suckers and can be a nuisance to humans and animals.
Who do black flies bite?
Normally, wild animals are among the typical victims of black flies. Grazing animals such as cows or horses, as well as smaller animals, for example dogs or birds, are also attacked by the parasites. Last but not least, humans are also popular hosts of black flies, especially when there is a lack of other hosts. The insects can hunt individually or in swarms. Body and sweat odors guide them to their hosts, and they fly the last stretch on sight. Black flies prefer thin areas of skin and like to bite the head and hairline as well as the arms and legs. While they cannot bite through clothing, they like to crawl under clothing at collar, sleeve, and pant openings.
Where are black flies found?
These mosquitoes are found in many parts of Germany, especially in the south, in the lowlands and along rivers. Depending on the subspecies, black flies are native to everywhere in the world. Black flies are often found around livestock pastures. An increased occurrence can also be found near flowing water, as this is where the mosquitoes lay their eggs. Blackfly larvae prefer to hatch in warm weather, so a hot summer can quickly result in a veritable plague of these mosquitoes. Black flies are not to be expected at ponds, lakes or puddles, as they breed exclusively in flowing water. Unlike mosquitoes, however, they do not fly into our living spaces, but attack exclusively outdoors, such as in the garden or while walking. They can fly many miles in search of prey.
When do black flies fly?
Depending on weather conditions, the insects are active from spring to fall, usually from May to September. They like warm, humid weather. In search of blood, females prefer to attack during the day, usually in the morning or late afternoon. Black flies are usually not very active in windy and lower temperatures.
What helps against black flies?
To protect against black flies, measures similar to those used to ward off mosquitoes are recommended. Consider the following tips:
- It is advisable to wear light-colored, long clothing with tight-fitting cuffs, closed shoes and headgear, which ideally also protects the hairline.
- Use insect repellents (ideally with DEET or icaridin).
- If necessary, always apply the sunscreen first and then the mosquito repellent, renewing the mosquito repellent after the duration indicated on the package.
- Open strollers should be covered with an insect net.
- It is also advisable to avoid the vicinity of streams and rivers and meadows where animals graze – especially in the morning and late afternoon.
The Ministry of the Environment in Brandenburg has published an information sheet for the Oder region, which is always affected, in which, in addition to other tips on insect repellent, there are also pictures of black flies.
What home remedies work against black flies?
Whether home remedies such as essential oils or coconut oil are suitable to repel or even kill black flies is controversial. The scent of catnip, lavender, lemongrass and rosemary is considered to repel mosquitoes – but if you are looking for a really effective remedy against black flies, you are better off using the chemical products. Unfortunately, traps to control the insects or blackfly larvae do not exist. The good news is that you are usually safe from black flies in your home, as they only attack outdoors.
