What Is A Silk Allergy?

Silk allergy refers to the medical condition where the affected person suffers from adverse reactions after coming into contact with silk or silk-related products.⁶ 

Sericulture is the process that involves the production of raw silk. Silk is a protein usually derived from silkworms, Bombyx mori. Silkworms are mostly fed with mulberry leaves. Some spiders also produce silk but are not of high enough quality for clothing. Silkworms have four development phases: ova, larva, pupa, and moth. Silkworms are caterpillars which make a cocoon during their transition phase from larva to pupa. After the transition, they break the cocoon open and come out. However, to produce silk, the cocoon should not break. For this reason, silkworms are put in hot water to kill them before they emerge from the cocoon. Filament from the cocoons is unwound to form silk yarn. The cocoon is bound together with the help of sericin.⁷ Silk obtained with sericin is called raw silk. It is processed to become the silk used in manufacturing clothes or for cosmetic purposes.¹

Causes of silk allergies

Silk allergy is caused due to the presence of proteins in the silk. Excrement, dander, and silk from the silkworm pupae are a known source of allergens. Silk is used not only in the textile and cosmetic industry but also as food. Silkworm pupae are a delicacy in some Asian countries such as China, Japan or Korea. 

Silkworm pupae contain two main proteins: fibroin and sericin.⁸ Sericin is considered the main allergen. Currently, there are 26 known allergenic proteins in silkworm pupae, whereas the larvae have one allergen - arginine kinase.¹ In Asian countries, food allergies associated with silkworm pupae are very common. 

Silkworms can cause three types of allergic reactions depending on the source or developmental stage.¹^,²

• Food allergy: Allergic reactions after consuming raw, boiled, or fried silkworm pupae. Tropomyosin from silkworms causes these allergic reactions 
• Contact allergy: Some people develop allergic reactions when they come in contact with silk-containing products
• Respiratory allergy: Inhaling silkworm moth particles in the air can cause respiratory allergies 

Uses of silk

Silk can be used for food, textiles, medicinal, and cosmetic products.¹^,²^,4

Textiles 

Silkworms produce silk which is a popular and luxurious fabric. They are also expensive and very strong. 

Cosmetic uses

Silk is a component of several cosmetic products. There are 7 silk proteins used in cosmetics.

Dietary uses

Let's check out the nutritional value of 100 g of silkworm pupae. Silkworm pupae have higher protein content compared to other animal-based foods. 

In Korea, silkworm pupae are boiled and seasoned to be sold as snacks. In China, silkworm pupae are roasted and eaten as snacks.

Other uses 

Apart from dietary, textile, and cosmetic uses, fibroin protein from silk can also be used for:

• Water absorbency
• Parachutes
• Surgical sutures
• Artificial blood vessels
• Tyre lining materials
• Dried silkworm pupae are used as a medication for relieving flatulence muscular spasms and as an expectorant

Symptoms of a silk allergy

Silk allergy can be a respiratory, food, or contact allergy. A study was conducted in the Ramanagara area, India on workers handling silk processing to determine the occupational hazards of sericulture. Many workers presented with allergic symptoms after a skin prick test.⁵

Another study was conducted on patients from a Korean hospital who presented with allergic reactions after being exposed to silkworm pupae. They also underwent skin prick tests. The study found that reactions occurred within 30 minutes of exposure.³ 

There can be different symptoms based on the silkworm's source and developmental phase.¹

• Urticaria: Also called hives. These are rashes or patches on the body with a stinging or burning sensation. They usually get better on their own in a few days. But, if symptoms persist, consult a dermatologist 
• Dizziness: Some people might feel dizzy after exposure to silkworms. 
• Skin itching: Some people experience itching all over their body after coming into contact with silkworms
• Asthma: Asthma is a respiratory allergy where the affected person has breathing difficulty. Apart from breathlessness, people can also experience coughing or a feeling of tight chest
• Allergic rhinitis: This allergic reaction is characterised by symptoms such as sneezing, itchy nose, runny or blocked nose, runny or itchy eyes, cough, and itchy mouth. Nasal sprays and antihistamines can help treat rhinitis. Contact a pharmacist for advice
• Allergic conjunctivitis: Also called red or pink eye. It affects both eyes, causing them to turn red with an itchy sensation. Other symptoms are watery eyes, pus, and a burning sensation. Wiping the eyes with boiled water after it cools down can relieve the symptoms
• Anaphylaxis: This life-threatening allergic reaction is characterised by swelling of the tongue and throat, difficulty in breathing and swallowing, wheezing, coughing, dizziness, or rashes. If you or anyone is having anaphylactic shock, call an ambulance 

Diagnosis of a silk allergy

Diagnosis for allergy is done by a skin prick test. The nurse will mark some letters on the forearm that signify different allergens (substances that cause allergy). Then a solution containing allergens will be dropped on their respective places. After that, the nurse will scratch each drop with a metal lancet. Then all the drops will be cleaned, and the patient sits in the waiting room for 15-20 minutes. The size of each allergic reaction will be noted, and doctors will prepare the treatment plan. This test is not painful. But, there might be small rashes, which might get better after some time. It is advised not to take antihistamines before the test. 

Treatment of a silk allergy

If you have a silk allergy, try to avoid wearing silk clothes and food or products containing silk. You can contact your GP for treatment options.  

• Steroids: Ointments and creams containing mild steroids can be used to soothe the rash, itching, or swelling
• Pills: In severe cases, pills or antibiotics can be prescribed to treat the rash or itching

Prevention of a silk allergy

If you have a known silk allergy, you can take certain precautions to prevent any possible allergic reactions. 

• Avoid wearing silk garments
• Avoid eating food containing silkworms
• Apply anti-itch cream or ointment

Summary  

Silk allergy refers to an allergic reaction after exposure to silk garments or consuming silkworm pupae. Silkworm pupae are a common snack option in some Asian countries such as China, Japan, or Korea as they have very high nutritional value and these countries report several cases of silkworm pupae allergy. 

Silk can also be used in textiles, food, medicines, and cosmetics. Symptoms of a silk allergy include urticaria, allergic rhinitis, allergic conjunctivitis, asthma, skin itching, dizziness, and anaphylaxis. Skin allergy tests or skin prick tests can help to diagnose a silk allergy. Steroid creams or antibiotics can be prescribed to treat silk allergy, depending on the severity of the allergic reaction.