Rhizopus nigricans is a fungus commonly known as bread mold and is the most common species of Rhizopus

Rhizopus

Rhizopus is a genus of common saprobic fungi on plants and specialized parasites on animals. They are found on a wide variety of organic substrates, including "mature fruits and vegetables", faeces, jellies, syrups, leather, bread, peanuts and tobacco. Some Rhizopus species are opportunistic agents...

. It is found on old food and in soils and even in children's sandboxes. The genus contains some 50 species and bread mold is sometimes confused with species of Mucor

Mucor

Mucor is a microbial genus of about 3000 species of moulds commonly found in soil, digestive systems, plant surfaces, and rotten vegetable matter.-Description:...

or other species of Rhizopus like Rhizopus oryzae

Rhizopus oryzae

Rhizopus oryzae is a fungus that lives worldwide in dead organic matter. An opportunistic human pathogen, it is one causative agent of zygomycosis . The RA 99-880 strain, which was isolated from a fatal infection, had its genome sequenced by the Broad Institute in 2004–2005. R...

. The spore

Spore

In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s, dispersed in hot dry weather, contain allergen

Allergen

An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....

ic protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s with 31 distinct allergens, which can produce respiratory and nasal symptoms in concentration (chronic cough, dyspnea

Dyspnea

Dyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...

, chest tightness, chronic phlegm, snuffle, snizzle and allergic rhinitis

Rhinitis

Rhinitis , commonly known as a stuffy nose, is the medical term describing irritation and inflammation of some internal areas of the nose. The primary symptom of rhinitis is nasal dripping. It is caused by chronic or acute inflammation of the mucous membrane of the nose due to viruses, bacteria or...

). Food handling workers are particularly at risk if they are mold allergic.