1. ALLERGEN AND PARASITE IMAGES

2. Scanning electron micrograph of a grain of marigold pollen. Credit: Annie Cavanagh/Wellcome Images Marigold pollen

3. Scanning electron micrograph of a single pollen grain from the common morning glory (Ipomoea purpurea), still sitting on the anther. This is used as a traditional Chinese medicine. Some varieties have hallucinogenic properties similar to LSD. Magnification 600x. Credit: Stefan Eberhard/Wellcome Images BIGPICTUREEDUCATION.COM Common morning glory pollen grain

4. Two grains of pollen from a lissianthus plant. Credit: Annie Cavanagh/Wellcome Images BIGPICTUREEDUCATION.COM Lissianthus pollen

5. Penicillium mould Scanning electron micrograph of Penicillium mould producing chains of spores. Credit: David Gregory & Debbie Marshall/Wellcome Images BIGPICTUREEDUCATION.COM

6. Asbestos fibres (silicate minerals) in human lung tissue. Inhalation of and prolonged exposure to asbestos fibres can cause lung disease, including mesothelioma (a type of cancer), pleural plaque and pleural effusion. Credit: Spike Walker/Wellcome Images BIGPICTUREEDUCATION.COM Asbestos fibres in a human lung

7. Dust mite Scanning electron micrograph of a dust mite on a dust particle. Dust mites feed on non-living organic material such as flakes of shed human skin. Dust mites are a common cause of asthma and allergic symptoms worldwide. Credit: Annie Cavanagh/Wellcome Images BIGPICTUREEDUCATION.COM

8. Light micrograph of human fleas (Pulex irritans). Found all over the world, human fleas are blood-sucking ectoparasites and can be vectors of serious diseases, such as plague. Male fleas (top) are smaller than females (bottom). Credit: Spike Walker/Wellcome Images Human fleas

9. Colour-enhanced scanning electron micrograph of Giardia lamblia, a commonly encountered water-borne intestinal parasite that causes diarrhoea. Credit: David Gregory & Debbie Marshall/Wellcome Images Giardia protozoan

10. Trichinella parasite A high-resolution image of the human helminth parasite Trichinella spiralis. Trichinella are the smallest roundworm (nematode) parasites of humans, affecting people around the world. Humans can be infected with Trichinella spiralis by eating infected meat, such as pork. Credit: David Linstead/Wellcome Images BIGPICTUREEDUCATION.COM

11. Ascaris lumbricoides is the largest roundworm parasite of humans, growing up to 35 cm long. It causes the disease ascariasis and can be found worldwide, though is far more common in tropical countries. Credit: Damien Schumann & University of Cape Town/Wellcome Images Ascaris parasites

12. Threadworms in the villi of the gut Threadworms (green), also known as Enterobius vermicularis, are tiny parasitic worms that hatch eggs inside humans and infect the large intestine. Two villi (finger-like projections) in the gut are shown here (brown). Threadworms are the most common type of worm infection in the UK, and are particularly common in young children: up to 40 per cent of under-tens are infected with threadworms at any one time. Credit: Annie Cavanagh/Wellcome Images BIGPICTUREEDUCATION.COM

13. Photomicrograph of a hookworm larva. Hookworms are bloodsucking roundworms that attach themselves inside the intestines using their hook-like mouths. It’s estimated that they affect over a billion people across the world, mainly in Africa, China, the Americas and South-east Asia. Magnification 100x. Credit: Mae Melvin/Centers for Disease Control and Prevention Hookworm larva

14. Segments of a tapeworm (Taenia saginata) extracted from a patient in East Africa. Taenia saginata is more common in less economically developed countries and is usually found in areas where cattle are reared, as it uses cows as an intermediate host. Credit: Nathan Reading/Flickr Tapeworm

15. Malaria-causing parasites Blood smear showing the presence of Plasmodium falciparum parasites, which cause malaria, in red blood cells. Credit: Spike Walker/Wellcome Images BIGPICTUREEDUCATION.COM

16. Scanning electron micrograph of a mosquito (Anopheles stephensi), showing the wing, proboscis, antennae, abdomen and legs. Anopheles stephensi is one of the major vectors of urban malaria in India and some parts of Asia. It is commonly used in research as it can be easily reared and maintained in the laboratory. Credit: Lauren Holden/Wellcome Images BIGPICTUREEDUCATION.COM Mosquito

17. Schistosoma, also known as blood flukes, are a genus of parasitic flatworms. They cause the disease schistosomiasis, which threatens hundreds of millions of people across Africa, Asia and Latin America. Schistosoma larvae live in fresh water and enter humans by burrowing through the skin. Once inside, the parasites move around the body as they develop (from the skin to the lungs and then the liver) before finally settling in the veins near the intestines and bladder. Credit: Wellcome Library, London Schistosoma parasites inside a blood vessel

18. Photomicrograph of calcified Schistosoma eggs in the bladder. Once mature, a female Schistosoma parasite begins laying eggs, which pass through the walls of its blood-vessel home and into the intestines or bladder. The eggs are then excreted back into the outside world, hatching in fresh water. Credit: Wellcome Photo Library/Wellcome Images Schistosoma eggs

19. Hatched Schistosoma parasites have to use an intermediate host – various species of freshwater snail – to complete the first stages of their life cycle. They then return to open water. Humans are therefore only at risk of infection where these snail vectors are present. Credit: Swiss Tropical Institute, courtesy of N Weiss/Wellcome Images Snails

20. A culture smear showing Leishmania parasites. These parasites cause the disease leishmaniasis, which can take three different forms: affecting the skin, the internal organs, or the mucous membranes of the mouth, throat and nose. Credit: Liverpool School of Tropical Medicine, courtesy of A Stich/Wellcome Images Leishmania parasites

21. A female phlebotomine sand fly feeding on the tail of a mouse. The fly’s engorged abdomen is filling with blood. Sand flies are responsible for infecting humans with Leishmania. Credit: Swiss Tropical Institute, courtesy of R Knechtli/Wellcome Images Sand fly

22. Reusing our images Images and illustrations All images, unless otherwise indicated, are from Wellcome Images. Contemporary images are free to use for educational purposes (they have a Creative Commons Attribution, Non-commercial, No derivatives licence). Please make sure you credit them as we have done on the site; the format is ‘Creator’s name/Wellcome Images’.Creative Commons Attribution, Non-commercial, No derivatives licence Historical images have a Creative Commons Attribution 4.0 licence: they’re free to use in any way as long as they’re credited to ‘Wellcome Library, London’.Creative Commons Attribution 4.0 licence The Flickr image that we have used in this gallery is available under a Creative Commons Attribution, Non-commercial, No derivatives licence. Creative Commons Attribution, Non-commercial, No derivatives licence Cartoon illustrations are © Glen McBeth. We commission Glen to produce these illustrations for ‘Big Picture’. He is happy for teachers and students to use his illustrations in a classroom setting, but for other uses, permission must be sought. We source other images from photo libraries such as Science Photo Library, Corbis and iStock and will acknowledge in an image’s credit if this is the case. We do not hold the rights to these images, so if you would like to reproduce them, you will need to contact the photo library directly. If you’re unsure about whether you can use or republish a piece of content, just get in touch with us at bigpicture@wellcome.ac.uk.bigpicture@wellcome.ac.uk