What Does Waxing and Waning Mean in Medical Terms?

In medical language, “waxing and waning” describes symptoms or a condition that periodically intensify (wax) and then subside (wane), cycling between worse and better phases without necessarily disappearing entirely. Doctors use the phrase to distinguish conditions that fluctuate over time from those that are steady, constantly progressive, or one-and-done. The pattern turns up across an enormous range of medicine, from autoimmune flares and psychiatric episodes to the fever spikes of certain infections, and recognizing it often changes how a condition is diagnosed, treated, and monitored.

The Basic Idea Behind the Phrase

“Wax” is an old English word meaning to grow or increase, and “wane” means to shrink or diminish. Think of the moon: it waxes from new to full, then wanes back again. In a clinical chart note, a physician who writes “the patient’s pain has a waxing and waning character” is telling the next doctor that the symptom is not constant. It swells, peaks, retreats, and may swell again. The cycle can be hours long, as with certain headaches, or stretch over months or years, as with many autoimmune diseases.

This is more than a poetic description. Whether a symptom waxes and wanes or stays flat carries real diagnostic weight. A rash that comes and goes points clinicians toward different causes than a rash that appeared once and never changed. Abdominal pain that rises and falls in waves suggests a different mechanism than a dull, unvarying ache. The pattern itself is evidence.

Autoimmune Diseases and the Flare-Remission Cycle

Autoimmune conditions like lupus, rheumatoid arthritis, and multiple sclerosis are among the most recognized waxing-and-waning diseases. In these disorders, the immune system attacks the body’s own tissues, but the attack does not proceed at a constant rate. Instead, periods of active inflammation (flares) alternate with stretches of relative calm (remission). Researchers have modeled this behavior mathematically, showing that the interplay between aggressive immune cells that damage tissue and regulatory immune cells that suppress them is enough to produce repeated flare-ups and periods of dormancy on its own, without any outside trigger being required.

One modeling study demonstrated that the cycle can be captured by just two biological functions: the immune response itself and the rate at which target tissue regenerates. When immune attack releases fragments of the body’s own tissue, those fragments stimulate both the attacking cells and the regulatory cells that rein them in. The regulatory cells eventually gain the upper hand and symptoms recede, but the balance is inherently unstable, so another flare can ignite later.¹ More recent computational work has framed autoimmune flares as “excitable” events, similar to the way a nerve fires: a small perturbation can push the system past a threshold and trigger a full episode, even when the perturbation itself is minor.²

For patients, this means that flares are not always caused by something identifiable like stress, missed medication, or a bad night of sleep. The immune system can cycle on its own, and the randomness of flare timing is a feature of the disease biology, not proof that the patient did something wrong.

Infectious Diseases That Relapse by Design

Some infections have evolved the waxing-and-waning pattern as a survival strategy. Relapsing fever, caused by Borrelia spirochete bacteria transmitted by ticks and lice, is the textbook example. Patients develop high fever, feel better for several days, then spike a fever again, sometimes cycling through multiple relapses. The bacterium pulls this off by continually changing the proteins on its outer surface, so by the time the immune system learns to recognize one version, the pathogen has already switched to a disguise the body has never seen.

Research on Borrelia hermsii, a common relapsing-fever species, has shown that these surface-protein switches, called antigenic variation, are what allow the spirochete to persist in the bloodstream through repeated immune attacks.³ Work on a related species, Borrelia miyamotoi, found that the genetic reshuffling happens within days of infection, even before the host has had time to mount an antibody response, meaning the organism is already preparing its next disguise before the first immune wave arrives.⁴

Malaria works on a similar principle. The Plasmodium parasite cycles through stages inside red blood cells, and the synchronized bursting of infected cells produces the classic every-two-or-three-day fever spikes that ancient physicians recognized centuries before anyone understood the cause. In both malaria and relapsing fever, the waxing and waning is not the patient’s body being inconsistent; it is the pathogen engineering its own rhythm.

Mental Health and Neurological Conditions

Psychiatric disorders are frequently described as waxing and waning, and this has been confirmed by long-term population studies. One epidemiological study tracking mental health syndromes over time found that diagnoses of mental disorders have a strong tendency to wax and wane, with people meeting diagnostic criteria during some periods but not others, rather than remaining consistently symptomatic or consistently well.⁵

Bipolar disorder is perhaps the most obvious example. Patients cycle between depressive episodes, manic or hypomanic episodes, and stretches of stable mood. A subset develop rapid cycling, defined as four or more mood episodes per year. One multicenter survey found that about one in ten patients met criteria for rapid cycling at a given assessment, and that risk factors for entering a rapid-cycling phase included certain comorbid conditions and specific medication profiles.⁶ The clinical challenge is that the waxing-and-waning pattern can make it hard to tell whether a treatment is working: did the patient improve because of the medication, or because the illness was naturally entering a wane phase?

ADHD, a condition most people think of as fairly constant, also follows a fluctuating course. Long-term follow-up data show that among people diagnosed in childhood, only a small fraction remain consistently symptomatic through adolescence and into adulthood. The majority, roughly two-thirds in one study, experience a waxing-and-waning pattern where symptoms partially remit, return, and shift in severity over the years.⁷ Full, lasting remission turns out to be uncommon, but so is an unwavering, stable course. Most people live somewhere in between.

In neurodegenerative conditions, waxing and waning can take on a different character. Lewy body dementia is specifically associated with cognitive fluctuations that can shift over hours, not just months. Patients may appear relatively sharp in the morning and profoundly confused by evening. Research using brain-wave recordings has linked these fluctuations to changes in how flexibly the brain switches between different activity states, with greater moment-to-moment variability in brain dynamics correlating with worse clinical fluctuation scores.⁸

Post-Exertional Malaise and Chronic Fatigue

People living with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or long COVID often describe their illness as one of constant waxing and waning, with a specific trigger that many other waxing-and-waning conditions lack. Post-exertional malaise, or PEM, is a delayed worsening of symptoms that follows physical or cognitive exertion, sometimes not appearing until a day or two later and lasting anywhere from a few days to several months.⁹

PEM is now considered a hallmark feature of ME/CFS and is increasingly recognized as a core symptom in long COVID as well.¹⁰ What makes this form of waxing and waning distinctive is that patients can sometimes identify the precipitating event. But the delay between the trigger and the crash, combined with the variable duration of each episode, makes the connection easy to miss. A person who feels fine during a grocery run but collapses with fatigue and pain two days later may not connect the two events, and a doctor unfamiliar with PEM may not think to ask.

The unpredictability of the wane phase is especially difficult. When experimental exercise tests are used to trigger PEM in a controlled setting, the onset tends to be more immediate, but the duration of the subsequent crash varies widely from person to person.⁹ You cannot simply predict when you will come out the other side.

The Body’s Own Daily Wax and Wane

Not every waxing-and-waning pattern signals disease. Your body has built-in cycles that fluctuate in predictable ways throughout each day. Cortisol, the hormone most associated with the stress response, follows a pronounced daily rhythm: it dips to its lowest levels at the start of sleep and climbs through the night, peaking right around the time you wake up.¹¹ This daily wax and wane prepares the cardiovascular system, the brain, and the metabolism for the shift between rest and activity.

When this normal rhythm is disrupted, such as in people who work night shifts, the consequences can be significant. The misalignment between the cortisol cycle and the demands being placed on the body has been linked to metabolic problems, cardiovascular disease, and impaired thinking.¹² Many symptoms that wax and wane over the course of a single day, such as joint stiffness that is worst in the morning, blood pressure that rises in the afternoon, or asthma that flares at night, owe at least part of their rhythm to these underlying hormonal and immune cycles.

Doctors sometimes use this knowledge diagnostically. If a patient reports symptoms that reliably worsen at specific times of day, that timing can narrow the list of possible causes. Morning stiffness lasting more than an hour points toward inflammatory arthritis rather than mechanical wear. Wheezing that peaks at 4 a.m. suggests an asthma component rather than a fixed airway obstruction. The timing of the wax matters.

Why It Matters for Diagnosis

The waxing-and-waning pattern creates a genuine diagnostic trap. If you see a doctor on a good day, your exam might look completely normal, and your complaint might be documented as mild or even doubted. If you see a doctor in the middle of a flare, the findings might be dramatic. Neither snapshot captures the full picture.

This is why conditions known for fluctuating symptoms, like lupus, Crohn’s disease, or ME/CFS, often take years to diagnose. The evidence is intermittent. Lab results drawn during a wane can be reassuringly normal, and a physical exam during remission reveals nothing. Clinicians experienced with these conditions know to weigh patient history heavily and to look for the overall pattern rather than relying on a single visit, but not every clinician has that experience, and many patients spend months or years bouncing between providers who each catch a different phase.

Patient-reported diaries and tracking tools are one response to this problem. In conditions like Sjögren’s syndrome, researchers have validated symptom diaries designed specifically to capture fluctuation. One study found that most patients considered even a modest change in diary scores meaningful, and that physicians preferred tracking individual item changes over time as the most useful way to detect a real shift in disease activity.¹³ The underlying principle applies broadly: if a disease waxes and wanes, a single measurement is not enough.

How Waxing and Waning Confounds Clinical Trials

The same fluctuation that makes diagnosis hard also complicates research. In a clinical trial, you want to know whether a drug actually reduced symptoms or whether the patient just happened to be entering a natural wane phase. This problem is especially acute in trials that target subjective symptoms like pain, fatigue, or nausea, where the disease itself is known to fluctuate.

Researchers studying this issue in supportive oncology trials have documented how multiple factors converge to inflate the apparent improvement seen in placebo groups. Among the culprits: regression to the mean (patients enrolled when symptoms are at their worst will naturally trend back toward average), patient expectations, and the inherent fluctuation of the symptoms being measured.¹⁴ Symptom chronicity and where a patient sits in their disease trajectory also matter: a patient enrolled during a flare is more likely to improve regardless of treatment than one enrolled during a stable phase.

This is one reason why crossover trial designs, where the same patient receives both the drug and the placebo at different times, are sometimes used for waxing-and-waning conditions. Each patient serves as their own comparison, which helps filter out the noise of individual fluctuation. Run-in periods, where patients are monitored for a stretch before randomization, can also help ensure that the baseline captures a representative snapshot rather than a momentary peak.

Drug Withdrawal and Rebound Effects

There is a related but distinct phenomenon that patients sometimes confuse with disease waxing and waning: rebound. When certain medications that act on the central nervous system are stopped abruptly, the body’s adaptations to the drug are suddenly unopposed, and symptoms can surge. This is not the underlying disease waxing; it is the nervous system overshooting its recalibration. The withdrawal syndrome typically produces effects that are roughly the opposite of what the drug originally provided.¹⁵

A person taking a sedative, for instance, may experience rebound insomnia and anxiety after stopping it. Someone discontinuing a blood-pressure medication may see a temporary spike that overshoots their pre-treatment levels. These rebound effects can look, from the outside, like a disease flare, but the mechanism is pharmacological, not pathological. The distinction matters because the appropriate response is different: rebound from drug withdrawal is usually managed by tapering the medication slowly, not by starting a new treatment for the disease.

Sorting out what is disease fluctuation, what is drug rebound, and what is coincidence is a recurring clinical puzzle. Patients and doctors both benefit from keeping in mind that waxing and waning can have multiple simultaneous causes, and that the timing of medication changes relative to symptom shifts provides the most useful clue.

Living With an Unpredictable Pattern

For people whose conditions wax and wane, the unpredictability itself is often cited as one of the hardest parts of the illness. Planning becomes difficult when you cannot reliably predict whether next Tuesday will be a good day or a bad one. The social consequences are real: canceling plans repeatedly, being unable to commit to work schedules, and facing skepticism from people who saw you functioning well last week and cannot understand why you are housebound today.

Symptom tracking, whether through a structured diary or a simple daily log, serves two purposes. It gives your clinician the longitudinal data they need to see the pattern rather than a snapshot, and it can sometimes reveal triggers or rhythms you had not noticed. Some patients find that their flares cluster around menstrual cycles, seasonal changes, or periods of disrupted sleep. Others find no pattern at all, which is itself useful information: it suggests that the fluctuation is being driven more by internal immune or neurological dynamics than by avoidable external triggers.

Treatment strategies for waxing-and-waning conditions often have two tiers. Maintenance therapy aims to reduce the overall frequency and intensity of flares, while rescue or acute therapy targets the flares themselves when they break through. In rheumatology, this might mean a daily immunosuppressant paired with short courses of corticosteroids for bad flares. In neurology, it might mean a disease-modifying drug for multiple sclerosis alongside symptom-specific treatments used as needed during relapses. The two-tier approach reflects the reality that waxing-and-waning diseases are not fully controllable: the goal shifts from eliminating symptoms entirely to managing the range of the fluctuation and recovering from flares more quickly.