July–August 2021

By Sarabeth Lowe, MPH Ms. Lowe is a Communication Specialist at the University of Delaware Disaster Research Center. Whether you’re riding in a car, flying on a plane, cruising on a boat, or floating through outer space, motion sickness can affect you. Kinetosis, the clinical term for the condition, is common and temporary, but nonetheless can make any type of travel a dreaded affair.1–9 Here’s what you need to know. Causes of motion sickness: Systems out of sync Despite how common it is, experts have not yet established the exact mechanism behind motion sickness.6–8,10–12 The most widely accepted theory is grounded in the sensory conflict and neural mismatch model, which describes 3 bodily systems becoming out of sync as a result of real (ie, physical) or virtual (ie, perceived) motion.11–13 In simple terms, our brains like to know and be able to anticipate what’s going on around us.2,3,5,7,8,10–12,14–17 If our brain can’t work out why our body is moving, this creates some internal confusion that disrupts the body’s normal routine. There are 3 key systems involved in motion sickness: Visual system (our eyes): This system is how we see the world around us. It sends the inputs it receives to the visual centers of our brain.12,18–21 Our eyes constantly perform automatic micromovements as we move through space. This response is called the vestibulo-ocular reflex (VOR).21–24 When you turn your head or experience any kind of motion, the VOR makes your eyes move in the opposite direction so that our visual field stays steady. This constant reflex helps maintain our gaze and stay balanced. Vestibular system (balance and motion): Our eyes are connected to our vestibular system, the sensory organs that allow your body to understand how you’re moving and how things around you are moving; it’s the system that helps maintain your balance or steadiness.7,12,21,25–27 In the case of motion sickness, the peripheral part of this system, which includes balance organs in your inner ear, is involved. Experts theorize that this system has the greatest influence on developing motion sickness.12 Proprioceptive system (the “sixth sense”): Proprioception is the automatic or subconscious process that signals to your brain where your limbs are without relying on visual input.7,12,16,28–30 For example, this is how your body adjusts the muscle tension in your feet and legs to maintain your balance and walk smoothly on an uneven surface. This awareness comes from multiple receptors around our body. When processing sensory information, the brain constantly monitors and stimulates these systems and specific reflex behaviors so we can function and perform everyday tasks. The efficiency of this anatomical integration is based on experience and outcome.2,5,7,8,11,12,31 It works well because our bodies have evolved so that these 3 systems—visual, vestibular, and proprioceptive—work in concert without any sensory conflict. The downside of this process is that our bodies are unprepared and ill-equipped for things with which it has no experience.4,12,16,26,27 Humans have not evolved as a species to drive on twisting roads, float through space, or experience virtual reality.12,26 With motion sickness, the vestibular system and our visual inputs are in conflict because they’re detecting different sensations. This can happen with real and perceived motion. A common example of this is focusing on a stationary object, like a phone or book, when riding in a car. The same can be said for someone wearing a virtual reality headset or watching an immersive 3D movie without moving. The body doesn’t know how to anticipate, manage, or de-escalate this neural mismatch.2,12,32 This releases a cascade of hormones and neurotransmitters that trigger symptoms of motion sickness—stomach awareness, nausea and vomiting, dizziness, low blood pressure, increased salivation, cold sweats, and pale, clammy skin.2–4,6,7,10,15,16,33,34 Motion Sickness Triggers Not all movement causes motion sickness. Research shows that low-frequency motion, which can be described as slow, sweeping, and rhythmic, typically triggers it. Movement can come from any direction; it can be vertical (up and down), lateral (side to side), reciprocating (forward and backward), and rotational (spinning).8,9,11,13,26,27,35,36 This explains why seasickness—where large, undulating waves cause slow, deep movement—is more common than air sickness, where the motion is generally smoother and steadier.16,19,31,34 The more pronounced the motion, the more likely symptoms will manifest. This theory also explains why active, anticipated movement, like pedaling on a bike to propel yourself forward or riding a horse, usually doesn’t cause motion sickness.12 Similarly, not all people are equally susceptible to it. Research shows that women tend to experience motion sickness more than men. This discrepancy may be due to hormonal fluctuations, such as those during pregnancy or certain stages of the menstrual cycle, that may increase susceptibility.10–12,36–39 Certain health conditions, such as vertigo and migraines, can make people more likely to experience motion sickness.26,27,36 Age also plays a role. Infants and young children typically do not experience motion sickness, but older children (especially those between 6 and 12 years of age) do. This upward trend levels off as people age into adulthood, as they learn the typical relationships between the body’s different senses and are able to contextualize their experiences.2,11,12,21,26,27,34,36,38,40,41 Treatment and Prevention Options Motion sickness is much easier to prevent than treat, and sometimes prevention isn’t possible. For the most part, symptoms will not cease until the movement stops.10,12,26,27,31,34,42,43 Most of the nonpharmacologic methods for easing motion sickness are behavioral, such as getting fresh air and taking deep breaths, or involve reducing or distracting from conflicting sensory input.9,12,15,27,31,34,38 The latter includes strategies such as sucking on hard candy or wearing acupressure bands. Though many of the products for managing motion sickness have mixed results on their physiological impact, research shows that the placebo effect can be a significant factor in treatment and prevention.10,27,31,34,42,44–48  Unfortunately, most drugs developed for motion sickness have significant side effects, such as drowsiness, and are only partially effective.2,10,12,31,49 Many experts concede that habituation is the most effective way to reduce motion sickness.2,4,7,15,16,27,31,34,35,43,45,50 However, this kind of desensitization isn’t always feasible because it can take weeks to achieve, is often stimulus-specific, and requires consistent re-exposure to

By Sarabeth Lowe, MPH Ms. Lowe is a Communication Specialist at the University of Delaware Disaster Research Center. Burns are likely one of the most common injuries worldwide.1–8 Burns go more than just skin deep; they are complex, dynamic injuries that activate numerous responses in the body; all have the potential to be physically and psychologically devastating no matter the size or severity.4,5,9,10 According to the World Health Organization, an estimated 180,000 deaths every year are caused by burns, and nonfatal burns are the leading cause of morbidity (ill health) worldwide.3 Roughly 600,000 people in the United States suffer from a burn injury each year, though estimates vary.11  A burn is a traumatic injury to the skin (and sometimes the underlying tissue) caused by contact with extreme temperatures, chemicals, radiation, or electricity.1,4,12–15 These causes have helped researchers develop 5 categories for burns: chemical, electrical, radiation, friction, and thermal.2,4,14–18 This article will focus on thermal burns, which occur upon contact with extreme temperatures.14,17,19,20 An Injury of Extremes Thermal burns can be caused by both hot and cold temperatures. Cold-induced injuries, like frostbite and ice burn, can also cause skin and tissue damage with lasting consequences. Research shows that the degree of tissue damage can be much more significant with frostbite because extended exposure to freezing temperatures can lead to ice crystals forming in the tissues. Cessation or reduced blood flow can lead to permanent damage to skin, muscles, and even bones.4,21–24 This lack of circulation is also why amputation is more common with cold-induced burns; dead tissue cannot be revived. Like heat-induced injuries, cold burns can cause irreversible, long-term, and devastating injuries. Types of Thermal Burns Thermal burns are categorized into 4 groups based on the source of injury. Contact. This kind of burn happens when your skin comes into contact with an extremely hot surface, such as a stove, car engine, or hearth. In many cases, these burns aren’t deep, but depending on the temperature and length of exposure, the heat can transfer quickly and damage the outer and sometimes deeper layers of the skin.1,25 These burns can happen in seconds and are likely the most common type of thermal burn. Flame. Flame burns happen when skin comes into direct contact with fire. They often occur in house fires, car accidents, during firework displays, when clothing catches fire, or at campfires. These burns can be severe because they affect deeper layers of tissue, larger areas of the body, and may damage the airway or lungs if smoke or heat is inhaled.1,26 Flash. Sometimes grouped together with flame burns, flash burns are caused by short, intense, usually indirect exposure to flame or a burning gas or vapor.1,16,27,28 They can be caused by flash fires, steam, or a minor combustion event (eg, when food “pops” when cooking on a grill). They can cause minor-to-major injury depending on the explosion’s strength.  Scald. A scald burn is caused by a hot liquid, such as boiling water, grease splashes, steam, or a beverage, coming into contact with the skin.1,29 These burns can happen in seconds, affect large swathes of skin, and cause long-term damage if not treated properly in a timely manner. Some researchers also consider electric burns, which are caused by contact with an electrical current or a strike through the body, thermal burns. These currents create heat in the body that can cause extreme internal and external damage.1,30 Though the skin damage may seem minor or invisible, electric burns can be life-threatening because they can affect deeper tissues, muscles, nerves, and the heart. Anatomy of the Skin Since thermal burns largely injure the skin, it is important to understand the skin’s composition. Skin is the body’s central sensory organ and first line of defense against infection or physical damage.4,31–34 Even at the skin’s thickest points (eg, soles, palms), it is still only a few millimeters thick..32 The skin has 3 layers.4,12,14,31,32,35 The outer, thinnest layer is called the epidermis. It continuously creates new cells in its lower layer to replace cells that are naturally shed from the skin’s surface. Underneath the epidermis is the dermis, the middle and thickest layer. It contains collagen and elastin, which support your skin’s overall structure; connective tissues; nerve endings; hair follicles; and sweat and oil glands.31,35,36 The innermost layer is the hypodermis. This fatty, subcutaneous layer is made up of connective tissue that cushions your muscles and bones.4,12,31,32,35 Burn Classification Healthcare providers consider several factors when evaluating a burn and use 2 specific variables to determine treatment: depth and size, measured as a percentage of the total body surface area (TBSA) affected.1,2,4,5,13,14,18,37–39 For decades, the degree system was the default mechanism for evaluating burns. However, this concept has slowly been phased out in the literature for determining morbidity and mortality,1,2,4,5,12,14,18,20,33,34 since it does not account for age, location on the body, pre- or co-existing health conditions, and—perhaps most importantly—inhalation injury from smoke or other fumes. For example, a minor 3-inch burn on the face of an adult may be easily managed at home, but one on an infant could have devastating consequences without treatment from a burn center. The current convention for classifying burns is based on how deeply the injury penetrates the layers of the skin. The American Burn Association (ABA) uses 4 categories to determine burn depth.11,18,40 Superficial. These burns only damage the epidermis. The affected area becomes red, sore, and might peel, but not blister. These burns are minor and can be treated at home. They usually heal within 5 days and do not scar. An example of this injury is a mild or moderate sunburn.11,18,40 Superficial partial-thickness. These burns reach in the dermis and may cause more significant pain, blisters, and swelling. Also considered minor burns, these injuries usually heal within 2 weeks and can be treated at home, though professional medical intervention may be needed depending on the size and location on the body.11,18,40  Deep partial-thickness. These burns involve damage to all 3 layers of the skin and may penetrate deeply