In order to survive, all living organisms must be able to separate themselves from their environment. They must be able to absorb nutrients from that environment, while at the same time protect themselves from injury and contamination. To ensure that we live safely within our environment, nature has evolved complex safeguards involving the nervous system, endocrine (hormonal) system, and immune system. As part of this defense system, each portal of entry into the human body has a sophisticated mechanism in place to provide this protection. While most of the time these defense mechanisms function flawlessly, there is the potential for problems; and several important disorders, including migraine, asthma and allergies, may reflect disruptions of these mechanisms. Disruption of the defense mechanisms designed to protect the lung can result in asthma. If those in the skin or sinus go awry, allergies can result, and if those involving the nervous system are disrupted, migraine can result.

People with migraine inherit a nervous system that is more sensitive to change than those without migraine. This nervous system evolved to be highly vigilant of its environment. When the migrainous nervous system is functioning well, this vigilance is often reflected in positive ways. For example, people with migraine are often well-organized, perceptive, and successful in school and artistic activities. This heightened vigilance may also be why migraine sufferers tend to be light sleepers and more emotionally vulnerable. However, if the nervous system perceives a threat from either the external or internal environment, the nervous system response can be an attack of migraine.

People born with asthma inherit a respiratory system that is more sensitive and vigilant of its environment than those without asthma. When the respiratory system of an asthmatic is threatened, it can respond dramatically by constricting the airways and initiating an inflammatory response in this defense perimeter. This results in wheezing and airway restrictions.

In a similar fashion, people with allergies respond in a variety of ways when their systems are threatened. The most dramatic is an anaphylactic reaction. This is the type of reaction noted rarely with a bee sting or an injection of penicillin and can be fatal. More commonly, allergic individuals develop sinus or skin symptoms that can vary considerably in severity. Seasonal allergies are likely the most common allergic condition. Symptoms generally consist of nasal congestion and discharge, eye irritation, and sometimes headache. Allergies can also be closely associated with asthma.

Observations that link these seemingly diverse disorders together include the fact that they are common in the general population, genetic factors appear to be important for all of them, each can be triggered by internal or external threats, and each represents an over-response or exaggerated response of the very mechanisms that nature designed to protect us. Given these similarities, it is not surprising that if you inherit one of these disorders, you have a greater likelihood of inheriting one or more of the others. In the recent American Migraine Study II, 40%-70% of respondents with migraine reported having allergies. Other studies have reported that people with migraine are 2 to 3.5 times more likely to have asthma, especially if they have a parent with migraine and asthma.

Unraveling the relationships these disorders have to each other poses many interesting questions. For example, can allergies or asthma trigger migraine? Clearly, these associations appear to be popular beliefs. For example, it has long been assumed that allergies are part of sinus disease and that sinus disease, in turn, results in "sinus headache." In fact, most participants in the American Migraine Study II who had diagnosed migraine also reported having "sinus headaches." However, whether sinus headache and migraine are distinct headache disorders or related to one another is a mater of debate.

This debate was the topic of a recent study presented at the American Academy of Neurology meeting in May of this year. Dr. Curtis Schreiber evaluated a group of people who reported they had recurrent attacks of sinus headaches. These individuals were self-diagnosed and had never been evaluated by a physician as having either sinus headaches or migraine. They reported headaches that were frequently one-sided and usually located in the area of the sinuses (around the eye or in the face). In addition, they often experienced nasal congestion and a clear nasal discharge during their headaches. Finally, many reported that changes in the weather could trigger attacks. It appeared that these factors are what made them believe their headaches were sinus-related.

After a careful history and examination, Dr. Schreiber asked this group of patients to keep diary records of their "sinus" headaches. After evaluating these diaries, he concluded that over 95% of these headaches actually met the criteria of the International Headache Society for the diagnosis of migraine. However, these headaches were also frequently accompanied by nasal symptoms and the pain was located in the sinus area.

In this group of self-diagnosed sinus headache patients, two other important observations were noted. First, these individuals experienced significant headache-related disability. In fact, the average score on the Headache Impact Test was 62, which is as high as the scores seen for many migraine patients who are receiving medical care. This indicates that these "sinus" headaches are not trivial or insignificant. Second, this population was using many different medications including sinus medications to treat their headaches, but most were dissatisfied with the effectiveness of their medications. Dr. Schreiber expressed concern that analgesic overuse could be a problem for these people, especially if these headaches are in fact migraine. Ongoing studies are now underway to look at the treatment needs for these headaches and to see if many of the headaches diagnosed as sinus headaches by physicians and the general public are really migraine.

The importance of this study is that it suggests a more than casual relationship may exists between migraine and "sinus" symptoms such as face pain and nasal symptoms. The nerve that conducts the pain impulses from blood vessels during migraine also has branches that go into the sinus cavities. It is possible that an allergic response activates this nerve system (the trigeminal nerve) that in turn develops into migraine. Conversely, it may be that in some migraine attacks the sinus branch of the trigeminal nerve is activated in the same manner as the trigeminal branches that supply blood vessels are activated. This activation could result in nasal symptoms being observed during migraine. Clearly further research is needed in this area.

The relationship between migraine and asthma is equally confusing. Clearly, there is some overlap in the risk or triggering factors for asthma and migraine--for example, stress and certain environmental exposures. Often migraine sufferers with asthma report that both asthma and migraine can worsen at the same time, and occasionally one seems to lead to the other. Dr. Fred Sheftell recently observed that a group of migraine patients who were given an asthma medication from a class of drugs known as leukotriene inhibitors to prevent asthma also had a reduction in the frequency of their migraine attacks. Consequently, he conducted a small research study using this asthma medication as a migraine preventive and reported it to be effective. Further studies are underway.

It is apparent that much more research is needed to fully understand the relationships existing among migraine, asthma, and allergies. Living with any or all of these disorders can be challenging. Management goals for migraine, asthma, and allergy are the same: minimize the frequency of attacks, rapidly control attacks once they have begun, preserve normal function as much as possible, and prevent the evolution from the episodic or intermittent form of these disorders into the chronic form. There are no cures, but there many effective therapies are available for each of these conditions. However, they work best when an individual understands the unique way his or her system interacts with its environment and is willing to develop a self-care lifestyle.

--Roger K. Cady, MD. Primary Care Network. Springfield, MO