Can Shoes Cause Allergies?
It's been awhile since we've posted here so let's jump into a topic that's not regularly discussed when we think about feet: allergic contact dermatitis or 'allergic eczema'.
The terms 'dermatitis' and 'eczema' are interchangeable, and generally describe a skin irritation/rash that can have various underlying causes. There are well-known external allergens, such as poison ivy, that can cause uncomfortable skin rashes with repeated contact, but did you know that shoes may also be a culprit?
'Shoe dermatitis' as it's often referred, describes an allergic skin reaction caused by any component of a shoe. The most common culprits are adhesives, rubber, fragrances, and dyes in fabrics/leather. Some notorious allergenic components include but are certainly not limited to:
-Potassium dichromate & chromium sulphate: used in leather tanning
-Formaldehyde: used as a leather stiffener and in tanning white leather; often found in resins/glues used to bond materials together
-Dimethyl fumarate (DMF): used in shoeboxes as sachets to prevent mold growth on leather shoes but is known to penetrate the leather upper of a shoe with prolonged exposure
-Nickel: commonly used in hardware and jewelry
-Dyes: paraphenylenediamene (PPD) in particular has been well-documented in cases of contact dermatitis. This textile dye is also found in hair dyes (many hair colourists have had hand dermatitis as a result) and dark henna tattoes
-Rubber boots or rubber toebox shoes: chemicals such as accelerators, used in manufacturing are typically the offenders here
It's important to note that people who suffer from excessive sweating or 'hyperhidrosis' have to pay closer attention to their feet and new footwear; excess sweat can actually cause certain compounds to leach out from shoe materials! This leaching effect can concentrate these chemicals and are more likely to have a sensitizing effect on skin.
As clinicians, it is very important that we rule out other similar-looking skin conditions such as tinea pedis (athlete's foot) or lichen planus (limiting autoimmune skin disorder). There are different markers that we assess, such as degree of itchiness and severity as well as location of the lesions, to help us make an accurate diagnosis. This is also why we love to take a thorough patient history, which can often give us the clues we need to make good decisions!
Here are some documented images of allergic dermatitis from footwear:
We always advise the public that if you wish to act preventatively, especially if you're susceptible to skin allergies, we always recommend:
Choose vegetable-tanned leathers or look for 'chromium-free' leather shoes
Double sock if needed: a thin sock layered with a thicker sock for those who can't avoid wearing i.e. workboots and are susceptible
Sock up!: it goes without saying, but you're less likely to have a reaction when wearing socks vs. without, so we tend to see more skin irritation cases in the summer. Also sock selection matters - athletic socks with wickable fabrics are better at managing sweat
Ensure a proper fit: Well-fitted footwear is less likely to cause blisters/hot spots or excessive sweating so visit your local comfort shoe store if you've never been fitted to proper footwear (Walking on a Cloud, Foot Sensation! etc)
Replacing rubber liners with foam or cork liners
Air out shoes regularly and dispose the sachets found in shoeboxes
Control excess sweat with anti-perspirant (i.e. Drysol)
If you notice a mild skin rash on your feet (or elsewhere), try these remedies at home:
-Avoid scratching the area
-Use cool, wet compresses to calm down the inflammation
-Apply anti-itch cream and take an oral anti-histamine tablet (i.e. Benadryl)
-Avoid touching the area as the allergen may be present on the affected skin
If you cannot manage this at home, you can certainly contact your nearest foot clinic and have a proper assessment performed. We hope this has given you some insight into the world of footwear and foot health!
Until next time, stay foot healthy!
Silvia & Chris
1. Image Source (1): https://dermnetnz.org/topics/shoe-contact-dermatitis
2. Image Source (2): https://www.researchgate.net/figure/Footwear-contact-dermatitis-from-dimethyl-fumarate-DMF-in-Case-2-patch-test-results_fig3_235713988