Fragrance Headaches: What's The Science Behind It?

Fragrances can cause headaches, with some people reporting subjective health issues such as migraines, headaches, and respiratory difficulties after exposure to perfumed products. While there is no solid evidence linking fragrance to headaches, researchers believe that certain fragrances can cause blood vessels in the brain to pulsate, resulting in headaches or migraines. In addition, odors can stimulate parts of the brain and nervous system responsible for head pain. This occurs when olfactory chemical irritants are transmitted by the sensory nerves, negatively affecting the trigeminovascular system, which is responsible for causing headaches.

Fragrance sensitivity and allergic reactions

Fragrance sensitivity can happen to anyone but is more likely if you have asthma or allergies. According to the National Eczema Association, fragrance sensitivity is present in 1–4% of the general population. Meanwhile, an international 2019 study noted about one-third of adults across the United States, Australia, the United Kingdom, and Sweden reported fragrance sensitivity.

A fragrance allergy, on the other hand, is when certain fragrance components called allergens come into contact with the skin, causing an abnormal immune reaction. This type of allergy generally causes symptoms on the skin, such as an itchy rash, that can be treated with medication. Up to 4.5% of the general adult population may be allergic to fragrance materials.

Symptoms of a fragrance allergy can include respiratory problems such as a feeling of suffocation, a stuffy or runny nose, and, in rare cases, anaphylaxis, a severe allergic reaction that can be dangerous. Skin problems such as hives and rashes are also common, as are cognitive problems, which may involve difficulty thinking clearly and concentrating.

It is important to note that not every skin reaction is due to an allergy. Only an allergen can cause a true allergy. If you are intolerant, as opposed to allergic, to a component of a fragrance, it will likely take a larger amount of that component to elicit a reaction.

Harmful ingredients like phthalates and parabens

Fragrances and perfumes are made up of dozens of compounds or synthetic volatile chemicals that create an odour. Some of these compounds can cross the blood-brain barrier and interact directly with receptors in the central nervous system, causing immediate changes in body functions, including blood pressure, brain activity, and pulse rate.

Parabens, on the other hand, are used as fungicides, bactericides, and preservatives in cosmetics, perfumes, and deodorants. Examples of parabens include methyl paraben (MP), butyl paraben (BP), ethyl paraben (EP), and propyl paraben (PP). Exposure to these chemicals has been linked to various health issues.

According to a study, the use of perfumes and colognes can lead to adverse health effects such as allergies, skin allergies, nervous system damage, migraine headaches, asthma attacks, mucosal symptoms, neurological problems, respiratory issues, and cardiovascular problems. Another study found that about 75% of people with shortness of breath have experienced asthma attacks caused by perfumes.

In addition, there are concerns about the effect of diethyl phthalate on male fertility, and exposure to parabens during pregnancy has been linked to dysfunction of the thyroid gland and weight gain in infants.

To avoid potential health risks, it is important to choose fragrance brands that are free from harmful chemicals like phthalates and parabens. Regulatory agencies like IFRA and the EU have lists of banned ingredients that cannot be used in fragrance products, but it is also important to educate consumers about the potential dangers of fragranced products.

The trigeminal nerve and nociceptive pathway

The trigeminal nerve is one of the cranial nerves. It is a key part of the trigeminal nociceptive pathway, which is a sensory pathway that runs from the nose and mouth to the brain.

The trigeminal pathway collects sensory signals from our head and carries them through nerve cells to the brain for processing. When this pathway is stimulated, it causes inflammation as it detects a threat that only the immune system can address. This immune response can lead to a headache.

Chemical smells such as formaldehyde, certain cleaning products, and cigarette smoke are known to act directly on the trigeminal pathway. These chemicals activate the trigeminal nerve endings in the nasal mucosa, leading to irritation, pain, sneezing, coughing, and glandular secretions.

The trigeminal pathway is also implicated in the trigeminovascular system, which can lead to a state of reactivity that lowers the threshold for pain. This system may also lead to allodynia, which is experiencing pain from a stimulus that does not typically cause pain.

Furthermore, the trigeminal nerve is involved in the release of calcitonin gene-related peptide (CGRP), which is a key mediator of neurogenic inflammation. CGRP causes vasodilation and serves as a chemotactic signal for inflammatory immune cells. Increased levels of CGRP have been associated with various types of headaches, including migraine and cluster headaches.

While the exact mechanisms of how odours trigger headaches are still being investigated, the role of the trigeminal nerve and nociceptive pathway is a crucial piece of the puzzle.

The trigeminovascular system and dural pain receptors

The trigeminovascular system (TVS) is a network of neurons originating in the trigeminal ganglion that innervates the cerebral vasculature, including the dura mater. It plays a role in pain transmission and vascular tone modulation, particularly in conditions like migraines. The TVS consists of trigeminal neurons, mostly from the ophthalmic division, and the blood vessels they innervate. The bipolar cell bodies of these neurons are located in the trigeminal ganglion, and their peripheral axons synapse with cranial structures and craniofacial blood vessels.

The activation of the TVS is associated with the headache phase of a migraine attack. This activation results in the release of vasoactive neuropeptides, such as substance P, CGRP, and neurokinin A, which lead to vasodilation and neurogenic inflammation. The TVS is also implicated in the development of throbbing pain and cephalic allodynia, which is an unpleasant sensation in response to innocuous stimulation.

The TVS has central projections to the thalamus, as well as connections with other pain processing and modulation centres in the brain, such as the rostral ventromedial medulla, periaqueductal gray, and locus coeruleus. These connections contribute to the generation of other symptoms associated with migraine, including nausea, photophobia, and osmophobia.

The exact mechanisms underlying the activation of the TVS during a migraine attack are still being elucidated. One hypothesis is the neurogenic inflammation hypothesis, which proposes that local release of inflammatory mediators activates meningeal nociceptors, leading to neurogenic inflammation. Another hypothesis is the cortical spreading depression hypothesis, which suggests that cortical spreading depression, a wave of neuronal excitation and inhibition, may activate meningeal nociceptors and trigger neurogenic inflammation in the dura mater.

Synthetic vs natural fragrances

Synthetic fragrances are man-made, whereas natural fragrances are derived from nature. Synthetic fragrances are typically more stable and affordable than natural fragrances, but they may have negative health and environmental impacts. Natural fragrances are generally safer, but some individuals may experience allergies or asthma due to certain natural ingredients.

Synthetic Fragrances

Synthetic fragrances are created in factories and laboratories, and they often aim to replicate the scents of natural plants. They are commonly used in commercial fragrances, including budget and high-end perfumes, as well as room sprays, candles, and diffusers. While they are more cost-effective and stable than natural fragrances, synthetic fragrances have been linked to various health issues.

Short-term exposure to synthetic fragrances may cause irritation to the eyes, nose, and throat, as well as nausea, dizziness, and headaches in sensitive individuals. Prolonged exposure may lead to more severe problems, including liver, kidney, and nervous system issues, as well as an increased risk of certain cancers.

Additionally, synthetic fragrances can negatively impact the environment. They contribute to air pollution by releasing volatile organic compounds (VOCs) and forming ground-level ozone, which harms ecosystems and wildlife.

Natural Fragrances

Natural fragrances are derived from natural sources such as trees, flowers, and other plants. Essential oils, oleoresins, distillates, and isolates are commonly used to create natural fragrances. Examples of plants that provide pleasant natural fragrances include lavender, lime, lemon, orange, clove, cedarwood, and anise.

Natural fragrances are generally safer for both people and the environment. They typically do not release harmful VOCs and have less negative impact on health and ecosystems. However, it is important to note that some individuals may experience allergies or asthma due to certain natural ingredients.

When choosing fragrances, it is essential to consider potential health and environmental implications. Reading labels, understanding ingredients, and opting for natural or synthetic fragrances based on personal sensitivities and preferences can help make informed choices.

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