There are some emotional and psychological conditions in which people are acutely aware of insects in their immediate environment, or imagine that they are being bitten or otherwise being affected by real or imaginary arthropods.

A heightened sense of fear of all arthropods, regardless of their potential to sting or bite is a condition known as entomophobia. This fear is usually not limited to obvious threats, such as wasps and spiders but often extends to all insects and related arthropods such as spiders. It may be a normal part of the behavior pattern of infants and young children to demonstrate fear and flight when confronted with spiders and other potentially arthropods and animals. However, this fear usually diminishes when the individual becomes an adult. When it does not and increases in intensity, it may be considered a phobia. There are levels of entomophobia, ranging from mild to severe, and there are some age and gender differences. Severe entomophobia is characterized by individuals being repulsed and frightened by the sight of even one arthropod, and the individual may become extremely fearful. This condition is not common, more often people have simply a mild dislike for insects. Treatment for severe entomophobia usually emphasizes greater understanding and familiarity with insects, and this may decrease the fear.

Most people do not like having insects and spiders in their living space, and some may express fear of their presence. These animals rank relatively high among the organisms that produce genuine fear in people; spiders are close behind bats and snakes in public dislike. Common fear is a natural extension of human experience, and is nearly universal in nature. Fear is, in fact, a reasonable and appropriate response to situations that involve potential danger and it has value in protection. However, persistent, irrational, and disproportionate anxiety in situations of only limited danger is a phobia (from the Greek phobos, meaning terror). For some individuals the presence of insects or spiders in their immediate surroundings produces an unreasonable level of fear, and this is considered entomophobia. In extreme cases this phobia can become so debilitating that the fear and time spent worrying often produces significant changes in lifestyle, and may result in even more personal suffering. The anxiety produced and degree of negative response in an individual with entomophobia ranges from strict aversion to terror.

Although many people respect the potential for painful injury and the health threat posed by wasps, ants (fire ants), and spiders, entomophobics do not have a logical basis for their fear and may be as apprehensive of a small ladybird beetle as they would be of an aggressive wasp. The unreasonable fear of insects is considered a simple phobia, and is just one of the common fears in human society, including fear of heights, closed spaces, bridges, etc. The general symptoms of simple phobia are characterized as sudden and intense feeling of apprehension, shortness of breath and increased heart rate, trembling, and sweaty palms. A key component of any phobia is avoidance; people that are extremely fearful of insects and spiders actively avoid them. Another component is the generalization of the fear to include other organisms, such as spiders (and spider webs), or to all insects that make a buzzing sound, whether a fly or wasp. The origin of insect and spider phobias has been a topic of considerable speculation and debate. For centuries it was believed that expectant mothers that were frightened by an insect passed their fear to the unborn child. A variety of other theories and myths of the causative factor of simple insect and spider phobias have been proposed. The prepotency theory suggests that insect and spider phobias have their basis in innate fears of various common and potentially harmful objects. Proponents of this theory contend that fear of these organisms provided survival advantages to early humans, and that present-day phobias are linked to the remnants of these fears. Evidence to support this theory may be seen in the fear of insects and spiders (and other animals such as snakes) that universally develops in early childhood, but usually diminishes with age. The survival value of such behavior would be significant. There would be a selective advantage to keeping children away from potentially harmful organisms until they had more experience and judgment.

An alternative theory for the cause of insect phobias suggests that fears of arthropods may be linked to aspects of their morphology, behavior, and their general characteristics. People with a fear of insects and spiders may dislike visual-appearance features such as small and compact body, long antennae, and unusual relation of eyes to head. Other visual cues eliciting a fear response are speed and unpredictable movement (such as found in cockroaches) and the appearance of being wet or slimy (such as mealworm larvae). The general conclusion of this theory is that animal characteristics that are divergent from human form or very unusual evoke aversion that may lead to fear.

Delusional parasitosis. The emotional condition in which a person believes that live organisms are present on or in the skin of his or her body, or periodically biting them is delusional parasitosis. This delusional conviction has been recognized in the medical literature for over a century. The condition is best defined as a false belief held in spite of invalidating evidence (delusional) that there are external or internal organisms (parasites) biting or stinging the skin. This emotional state may develop quickly and persist for months or even years. It is believed that delusions of infestation is more common with advancing age, and there is a female preponderance of about 2 to 1. Many sufferers consult entomologists, parasitologists and hygienists before seeking medical help. Even when a medical opinion is sought, it is usually a dermatologist who is consulted; psychiatric referral is often refused.

Some people have a history of genuine infestation of some insect or mite. However, this is uncommon. The cause of this syndrome may be a combination of factors. for example, delusional infestations occur in a wide variety of illnesses, both physical and psychiatric. Physical conditions have included diabetes mellitus and hypothyroidism. The psychiatric conditions associated with delusions of infestation include schizophrenia and depression. Toxic psychoses, in particular cocain psychosis (`cocaine bug'), are recognized as causes. Among the chronic organic brain disorders that cause delusional infestations are brain tumors and Alzheimer's disease. For many individuals the actual cause of the condition may be difficult to determine, but their conviction of its reality is genuine.

Victims of delusional parasitosis are typically well educated, often professional people (including pest control personnel) that are able to articulate their condition and provide a clear history and detailed description of the supposed parasite. Individuals typically characterize their condition or the supposed parasites as 1) black or white "bugs" (usually referred to as mites), that can change color when on different parts of the body; 2) the "bugs" crawl on the skin for short periods, sometimes tunnel in the skin, or jump on and off the person, typically from furniture, bedding, carpeting, walls, newspapers, and turfgrass outdoors. The origin of the "bugs" can be almost any household material, including some unusual items such as toothpaste and cosmetics; 3) the "bugs" may infest any portion of the body including hair, arms, legs and genital region; most commonly the infestation will be centered in areas that are within reach of their hands; 4) the "bugs" bite or sting, and often cause intense localized pain on the skin, scalp, and sometimes the eyes; sometimes papule-like irritations develop on the skin in response to the supposed bite or sting; the typical response to the pain or itch is prolonged scratching and in severe cases the skin is probed with sharp objects to the degree of causing tissue damage; 5) the infestation can be perceived to be so severe that the person leaves the house seeking relief, but the "bugs" usually reappear in the new location after a few hours or days; 6) the description of the supposed parasite is usually detailed and includes shape, color, and the presence of legs; the descriptions are usually related to the shape and habits of mites.

Persons suffering form this disorder are sincere and sometimes adamant in their belief of a parasitic-like organism causing their discomfort. They typically make attempts to catch the "bug" with adhesive tape applied to parts of their skin, or by scraping, gouging or otherwise removing parts of their skin for observation under a microscope. These samples usually consist of lint, strands of cloth, scabs, skin scales (dandruff) and other miscellaneous debris. Occasionally there will be fragments of insects in these samples. Careful examination of these samples and reporting no parasites were found is usually not accepted as invalidating proof. The resolution of delusional parasitosis may come with the realization that there is no parasite involved, or with a change in the situation that may have caused the problem.

Delusional dermatitis. Persons suffering from the sensation of itching, or a prickling, tingling, or creeping sensation of the skin (paresthia) often have the delusion that they are sensing the presence of mites. The supposed mites are often called "cable mites" or "paper mites", and they are assumed to be associated with the wires that supply electricity to computers and other equipment or with paper that accumulates in offices or storerooms. Cable or paper mite dermatitis is a delusory parasitosis in the sense that the victims may believe they are being exposed to the mites, even though these mites do not exist. People with delusional dermatitis (claiming either cable or paper mite) may be affected by some real substance in their environment. Identifying and eliminating the substance causing the sensations on their skin usually resolves the problem.

An itch on the skin is a sensation which is sometimes described as a mild form of pain. However, there is evidence that an itch is a separate sensation from pain, despite some similarities. The sensation of itching apparently results from some form of chemical or physical stimulation of receptors at the skin level. Itching is a subjective complaint, which may or may not be accompanied by a visible stimulus on the skin. The causes of itches are many and range from those which are not visible, such as those arising from diabetes, to the obvious burrowing of the skin by scabies mites. Other causes include irritants such as laundry detergents and fabric softeners, and the chemical used in fabric sizing and finishing, and occasional dry skin.