Sensitive skin

Have you ever felt your skin burning, itching or stinging after application of your favourite floral-scented cream? Did you end up with reddened skin, dryness or even scaling when you kept using it? You shouldn’t worry that much. Just pay more attention to the products you choose, as it seems you belong to the nearly 50% of the total population that suffers from skin sensitivity ¹. In epidemiological surveys in the US, 52% of women professed sensitive skin, while in the UK 51.5% of women and 38.2% of men claimed some form of skin susceptibility ². Statistics like this are quite awakening. However, which skin is defined as sensitive?

Definition of sensitive skin

Sensitive skin is a condition of cutaneous hyper-reactivity to a wide range of stimuli including cosmetics, toiletries, drugs, household cleaners, clothing or changes in the weather conditions. Although visible and objective signs of skin irritation are often absent, it is accompanied by abnormal sensory responses that influence the lives of those it affects ³,⁴,⁵.

What is the clinical picture of sensitive skin?

The clinical picture is still vague; there could be signs of reddened or swollen skin, scaling, papules, dryness, or scratches as well as sensory symptoms like burning, itching, pain, tightening and stinging. Symptoms can vary in kind and severity and there is usually a close time correlation with the exposure to the responsible stimuli ⁶,⁴.

Why does the sensitive skin react to chemicals?

The actual pathophysiology of what is happening at a cellular lever in the skin when there is sensitivity remains unknown ⁷. Scientists have given only some possible explanations on the physiological causes of sensitive skin and the effects that chemicals have on it. You may already know that the stratum corneum is the outermost layer of the epidermis that protects the underlying tissue from infection, dehydration and chemicals.  Hyper-reactors have been found to have a thinner stratum corneum accompanied with an imbalance of the normally existing lipids between the cells. As a result, there is an increased penetration of some chemicals ³,⁸. When the irritant chemical comes in contact with the deeper layers of the epidermis, skin cells respond with a variety of inflammatory hormones called cytokines and chemokines. These hormones bind to specific receptors on target cells and activate the production of some other hormones which may cause “vasodilation” ⁹. “Vasodilation” is the widening of blood vessels that enhances the transport of several immune agents intending to fight the irritant invader. Although it is a healthy response of our body, the outcome on our skin is redness and swelling. Cytokines may also cause the release of “neurotransmitters” such as the substance P and the calcitonin gene-related peptide that mediate the invasion sign. However, at the same time neurotransmitters stimulate the cutaneous nerve endings that are specialised in pain, heat and itch transmission resulting in a plethora of undesirable sensations such as pain, itching, burning or stinging ¹⁰,¹¹,¹².

Which chemicals affect the sensitive skin?

Skin-care product manufacturers have responded to the great numbers of people claiming sensitive skin with a plethora of products designed for them. Unfortunately, those products are not regulated regarding efficacy and safety letting traders make claims overestimated, invalid and illogical. The cosmetics market is awash with products which provide no evidence for the effects they promise to be having on sensitive skin. At the same time, the consumer with self-assessed sensitive skin has no clue which product could be harmful or beneficial ⁵. To help you become acquainted with products that could have a deleterious effect on your sensitive skin we have prepared a guide listing the guiltiest ingredients used in formulas of your favourite brands.

1. Fragrances

Fragranced consumer products are pervasive in society; Just think that more than 2,500 fragrance ingredients are currently used. Having the ability to produce a pleasant scent or mask unpleasant odours, they may be found everywhere from toiletries, cosmetics and cleansers till textiles, air fresheners and toys ¹³. Their nature may be natural, nature-identical, or completely synthetic ¹⁴. However, little is known about the composition of these products due to the complexity of formulations and lack of restrictions on ingredient disclosure ¹⁵. Their small size and highly lipophilic nature account for their irritating ability; they are capable of penetrating even intact skin ¹³ usually causing rashes to the face, hands and axillae ¹⁶,¹⁷. Common fragrances that are to blame for skin irritation are:

• Amyl cinnamal
• Cinnamyl alcohol
• Evernia prunastri (oak moss)
• Evernia furfuracea (tree mass)
• Eugenol
• Geraniol
• Hydroxycitronellal
• Iso-eugenol
• Alpha-isomethyl ionone
• Amylcinnamyl alcohol
• Anisyl alcohol
• Benzyl alcohol
• Benzyl benzoate
• Benzyl cinnamate
• Benzyl salicylate
• Citral
• Citronellol
• Coumarin
• d-limonene
• Farnesol
• Hexyl cinnamal
• Hydroxyisohexyl-3-cyclohexene
• Carboxaldehyde (Lyral)
• Butylphenyl methylpropional (lilial)
• Linalool
• Methyl heptine carbonate ¹⁶.

2. Preservatives

Preservatives are added to formulations that contain water in order to restrict the growth of micro-organisms which may harm the consumer or degrade the product. After fragrances, they are the second most responsible for cosmetic allergic contact dermatitis ¹⁶. Skin irritation is reported to vary with the combination of preservatives and the type of formulation ¹⁸. In any case, preservatives that should be avoided from people with sensitive skin include:

• Methylchloroisothiazolinone (MCI)
• Methylisothiazolinone (MI)
• Methyldibromo glutaronitrile
• Formaldehyde
• Quaternium-15
• DMDM hydantoin
• Diazolidinyl urea
• Imidazolidinyl urea
• Bronopol
• 2-Bromo-2-nitropropane-1,3-diol
• Iodopropynyl Butylcarbamate
• Benzyl alcohol
• Chloroacetamide
• Chlorphenesin
• Phenoxyethanol
• Triclosan
• Paraben esters (methyl, ethyl, propyl, butyl, benzyl)

Parabens are most usually encountered preservatives in marketed cosmetic products and there are many surveys that support their safety even for people with sensitive skin. it is indisputable, though, that their tolerance is related to their concentration, the frequency of use, site of application and skin status ¹⁹,²⁰,²¹.

3. Excipients

Many excipients common in dermal cosmetic and pharmaceutical preparations are likely to induce sensitisation. Typical examples are wool and fatty alcohols, propylene glycol and surfactants. Lanolin and lanolin derivatives such as hydrogenated lanolin, lanolin alcohol, wool fat and wool wax alcohols are employed as emollients and emulsifiers. Some people use them for treating varicose ulcers and stasis dermatitis but they often exhibit allergic reactions. Others with normal skin, though, rarely experience any adverse effects ²²,¹⁶,²³. Propylene glycol is widely used in household products and numerous cosmetic or pharmaceutical preparations. It may cause irritant/allergic contact dermatitis and subjective or sensory irritation ¹⁶,²⁴. Surfactants are present in almost every skin-care product. They remove dirt, sweat, sebum, microorganisms and dead cells from the skin but may also harm the natural proteins and lipids that comprise it. Cosmetic companies advertise a wide range of detergents as “very mild products”. However, since there is no international agreement on this characterisation, even those products may contain aggressive components. Surfactants inappropriate for sensitive skin may be:

• Sodium Lauryl Sulphate (SLS)
• Sodium Laureth Sulphate (SLES)
• Ammonium Lauryl Sulphate (ALS)
• Cetrimide
• Cetyl trimethyl ammonium bromide

On the contrary, gentle surfactants include:

• Sodium cocoyl isethionate
• Amphoacetates
• Coco glucoside
• Lauryl glucoside
• Decyl glucoside
• Cocamidopropyl betaine (free of impurities) ²⁵,²⁶

4. Dyes

  Allergic reactions can occur from all kinds of hair dyes; i.e. permanent oxidative, semi-permanent, and temporary, but are more common with permanent dyes ¹³. Søsted et al, examined 229 substances used in marketed products and found that 75% of them were strong/moderate sensitisers, 22% were weakly sensitisers and merely 3% were non-sensitising. Hair dye sensitisation can be a serious occupational hazard for hairdressers and beauticians and can lead to severe clinical reactions such as swelling of eyelids, face and scalp ¹³,¹⁶. Examples of irritating hair colours include:

• 1-Hydroxy-3-nitro-4-aminobenzene
• 1-Hydroxyethylamino-3-nitro-4-aminobenzene
• Basic Blue 99
• Henna
• N-(b-Hydroxyethyl)-2-nitro-4-hydroxyaminobenzene
• Pyrocatechol
• Resorcinol
• Toluene-2,4-diamine
• Acid Violet
• 2-Amino-6-chloro-4-nitrophenol
• 4-Amino-3-nitrophenol
• Disperse Violet
• HC Red
• HC Blue
• Picramic Acid
• 2-Amino-3-hydroxypyridine
• 3-Nitro-p-hydroxyethylaminophenol
• 4-Amino-2-hydroxytoluene
• 4-Amino-m-cresol
• 4-Hydroxypropylamino-3-nitrophenol
• m-Aminophenol
• N-bis(2-hydroxyethyl)-p-phenylenediamine
• o-Aminophenol
• p-Aminophenol
• 1-Naphthol
• 2,7-Naphthalenediol
• 2-Methyl-5-hydroxyethylaminophenol
• 2-Methylresorcinol
• 4-Chlororesorcinol
• p-Methylaminophenol
• Resorcinol
• 1-Hydroxyethyl-4,5-diaminopyrazole sulfate
• 2,4,5,6-Tetraaminopyrinidine
• 2,4-Diaminophenoxyethanol HCl
• p-Phenylenediamine

On the other hand, extremely weak sensitisers or non-sensitisers are:

• 6-Dimethoxy-3.5-pyridinediamine
• 2-Hydroxyethyl picramic acid
• Basic Red 22
• Basic Yellow 11
• N-Dimethyl 2.6-
• Pyridine diamine HCl
• N-Methoxyethylp-phenylenediamine HCl ²⁷,¹⁶,²⁸

5. Antioxidants

Antioxidants are added to cosmetics to limit degradation of unsaturated fatty acids and form only a minor group of cosmetic irritants. Examples include propyl gallate, which cross-reacts with other gallates and t-butyl hydroquinone, a commonly used allergen in the UK.  Moreover, sodium metabisulfite, used in oxidative hair dyes can cause allergic reactions to clients and hairdressers. Other common oxidants are:

• Butylated hydroxyanisole (BHA)
• Butylated hydroxytoluene (BHT),
• t-butyl hydroquinone
• Gallates (dodecyl, octyl, propyl)
• Tocopherol and its esters ¹⁰,¹⁶,²⁹

6. Active” or Category-Specific Ingredients

• Bleach and permanent-wave solutions

Persulfates that are used in bleaches, as well as glyceryl monothioglycolate and glyceryl thioglycolate which are used in permanent-wave solutions,  sensitise consumers and are a serious occupational hazard for dermatitis in hairdressers ³⁰,³¹.

• Nail cosmetics

Nail cosmetic products such as nail lacquers may contain tosylamide/formaldehyde resin while artificial nail preparations may be based on epoxy and (meth) acrylate compounds. These ingredients may cause reactions to both manicurists and their clients. 80% of all reactions are observed on the face, neck and eyelids ³²,¹⁰,¹⁶,³³,³⁴.

• Sunscreens

Allergy to sunscreens is uncommon but not rare. Active agents used to protect our skin from UVA and UVB radiation may cause contact allergy and photocontact allergy especially to people with sensitive skin. Such sunscreen allergens are:

• Benzophenones
• Cinnamates
• Salicylates
• Dibenzoylmethanes
• Anthranilates
• Methylbenzylidene Camphor
• Octyl Triazone
• 2-Phenylbenzimidazole-5-Sulfonic Acid
• Octocrylene

Zinc oxide and titanium dioxide have not been reported to cause allergies and thankfully, they are very popular with cosmetic manufacturers ³⁵,³⁶,³⁷.

 

• Insect repellents

Irritant skin effects such as redness of the skin and desquamation have been reported after the use of insect repellents. These products contain N-diethyl-meta-toluamide (DEET) or other chemicals that prevent bites from a wide range of insects and should be used frugally ³⁸.

7. All-purpose cleaners

Besides products for cosmetic purposes, regular use of chemically-based household cleansers can also leave your hands dry and flaky. Window and glass cleaners, dishwashers as well as products designed to remove stains from porous surfaces may include ammonia, isopropanol or trisodium phosphate. All these can cause your skin to burn and itch ³⁹,⁴⁰.

Factors contributing to the reaction of sensitive skin

It would be quite easy to advise you to stop using any of these possibly exacerbating ingredients. However, most of us consider beauty products a necessity in our everyday lives and these kinds of substances tend to be almost everywhere. Switching to chemical-free products is a very good alternative if you find a brand that you can really trust. Nevertheless, in case you cannot say goodbye to your beloved face cream or perfume, bear in mind that although the chemical nature of the ingredient plays a pivotal role in terms of skin sensitivity, there is a number of other factors that can determine whether your skin will be irritated or not.

• Frequency of application

It is true that the concentration of a potentially irritant ingredient in a single product may not be high enough to cause side effects. However, if you use cosmetics several-times-a-day, chances are that this ingredient will accumulate in your skin reaching a concentration that may cause adverse reactions. Moreover, you should not forget that most brands are using similar ingredients into their different products. Care should be taken, therefore, of the frequency that an ingredient is present in your daily routine, especially if you are using products of one particular brand.

• Composition

One of the safest ways to create a “hypoallergenic” product is to keep the formula simple. The fewer the constituents you see on the label, the lower the chance of synergism and skin reactions to one of them.

• Concentration of ingredients

Low concentrations do not guarantee safety. However, the possibility of sensitisation depends also on the concentration of the irritating agent.

• Application site

Contact sensitisation occurs more often on sensitive skin areas such as the lips, neck and eyelids or areas where the body folds like axillary or inguinal. Consequently, more attention should be paid to the choice of cosmetics you apply on those sites.

 

• Condition of the skin

Application on a damaged skin increases penetration of chemicals and the risk of skin sensitisation. As a consequence, if you intend to use a hand cream for dry hands or a product to alleviate atopic skin, make sure of the good quality of the ingredients included ⁶.

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