Similar to several other animals, camels have 3 eyelids on each eye. An eyelid is a fold of skin that covers and protects the eye. Humans, for example, have only 2 eyelids.
In camels, the upper and lower eyelids that guard the eye are thick, large, and are located in front of the eyeballs. The outside surface of these two eyelids is covered by skin and the deep surface is covered with conjunctiva, a sheet of the mucous membrane. 
These eyebrows have eyelashes on them. Eyelashes of the upper eyelid are long and tufted, and mostly located in the middle parts of the eye. Eyelashes of the lower eyelid are shorter and gradually disappear towards the lateral cantus (corner of the eye where the upper and lower eyelids meet). 
When a camel blinks, the upper and lower eyelid pass over the eyeball and spread tears to moisten and protect it from external effects. The eyelids will move vertically, from top to bottom and vice versa.
The third eyelid, also known as the nictitating membrane, is thin, large, triangular in outline, and well developed in camels. It is a translucent membrane that can be moved horizontally across the eye (from left to right). Unlike the upper and lower eyelid, the third eyelid does not have muscles that move it actively; its position is controlled by the position of the eyeball. The third eyelid in camels is between 1.37 and 1.57 inches long (3.5 and 4 cm) and between 0.76 and 0.85 inches wide (1.93 and 2.15 cm). 
There are two glands associated with the third eyelid, the superficial and deep glands. They are considered an important part of tear production.
Why Do Camels Have 3 Eyelids?
Camel’s eyelids are important for the production and distribution of tears, the removal of dust and debris, the protection of the camel’s eye, and possible important immunologic functions.
Because they live in some of the hottest areas of the world, wind and the sun can quickly dry out camels’ eyes. The glands in the camel’s eye will excrete tears to lubricate the animal’s eyes and keep them moisturized. When the camel blinks, its eyelids will evenly dispense the lacrimal fluid over the eyes. The length of their eyelashes (⅓ of the width of the eye) has been calculated as the ideal to divert the airflow away from the eyes, and thus prevent demoisturization.
Something that is not missing in the desert, besides the wind, are various dust particles and debris. Stronger winds might carry these particles straight into the camel’s eyes. The third eyelid works like a windshield wiper and removes any particle that got into the camel’s eyes. This nictitating membrane allows the camel to keep its eyes open during a sandstorm and walk freely, as it works as a barrier, and protects the eye.
Camel’s eye is constantly exposed to different environmental pathogens and can be particularly vulnerable to infections. Evolution has provided the eye surface with several defense mechanisms, with many of them operating through the tear fluid.
Immunoglobulin A (IgA) plays an important role in defense against invading micro-organisms in the eye and can influence the effect of some antibacterial factors in secretions, such as lactoferrin, lysozyme, defensins, and lactoperoxidase. These are all active substances that fight off different bacteria and viruses. A study from the Institute of Anatomy and Physiology has shown that IgA-positive plasma cells are located in some compartments of the third eyelid, which adds to the eyelid’s important protective function.
Granted, this was done on several domestic animals that have a third eyelid (not camels); but a similar situation may be with camel tears and their eyelids. More studies are required when it comes to the immunological function of the camel eyelids.
This concludes our article on the question “how many eyelids do camels have“.
Camels have 3 eyelids in total. The upper and lower eyelid is covered in long eyelashes and move vertically. The third eyelid is translucent, moves horizontally, and removes debris from the camel’s eyes. It might also have a part in fighting different diseases or infections.
 Ibrahim, Amira. Morphology And Morphometry of The Eyeball And Its Appendages of The Dromedary Camel. Diss. UOFK, 2007.
 Abuagla, I. A., H. A. Ali, and Z. H. Ibrahim. “An anatomical study on the eye of the one-humped camel (Camelus dromedarius).” International Journal of Veterinary Science 5.3 (2016): 137-141.
 Al-Ramadan, Saeed Y., and Abdelhadi M. Ali. “Morphological studies on the third eyelid and its related structures in the one-humped camel (Camelus dromedarius).” Journal of Veterinary Anatomy 5.2 (2012): 71-81.