DAN Medics and Researchers Answer Your Dive Medicine Questions
I have been diagnosed with mast cell activation syndrome (MCAS). Will that increase my risk of decompression sickness (DCS) if I dive?
With MCAS, mast cells release excessive amounts of histamine and other chemicals, leading to symptoms such as inflammation, hives, and systemic allergic reactions. While there’s no direct evidence linking MCAS to an increased DCS risk, some associated factors could influence that risk.
MCAS triggers chronic inflammation, which is a suspected factor in DCS development. An existing inflammatory state might exacerbate the physiological impact of nitrogen bubbles, increasing the risk of DCS symptoms. Also consider how the side effects of medications used to treat MCAS might interfere with diving.
MCAS may also cause systemic allergic reactions triggered by common environmental factors such as cold, new foods, pressure, stress, vibration, sunlight, or exercise. These reactions could lead to dizziness, low blood pressure, cough, nausea, vomiting, eye redness, airway swelling, abdominal pain, syncope, wheezing, mild subjective mental status changes, congestion, gastrointestinal disturbance, rash, joint pain, and fatigue. Most of these reactions could mask or mimic DCS symptoms, making diagnosis and treatment more difficult.
Before diving, people with MCAS should consult with a doctor familiar with their condition and a dive medicine specialist, who can assess individual risks and recommend strategies to reduce DCS risk, such as avoiding known triggers, controlling inflammation, and adhering to conservative dive profiles. Proper management of both MCAS and dive risks is key to ensuring a safe experience.
— Shannon Sunset AEMT, NCPT
I was recently diagnosed with Addison’s disease. Can I still dive?
Each case of Addison’s disease, or primary adrenal insufficiency, is vastly different and requires individual evaluation for medical clearance to dive. It has a variety of causes — including autoimmune diseases, infections, and cancer — and often the cause of Addison’s can be a bar to diving.
Most concerns related to adrenal insufficiency and diving pertain to resulting physical and physiological challenges, such as reduced exercise tolerance or the potential to lose consciousness due to postural hypotension. Symptoms such as low blood pressure and low blood sugar while in the water are problematic — even more so if unexpected dive conditions such as surge or choppy water were to occur.
Other possible symptoms, such as extreme fatigue or muscle and joint pain, can mimic DCS symptoms, making a correct diagnosis challenging. Medications used to treat Addison’s disease may carry additional considerations as well.
DAN recommends that individuals with Addison’s disease refrain from diving until they have been evaluated and cleared to dive by a physician trained in dive medicine or at minimum your treating physician in consultation with a dive medicine physician. DAN’s medical department can consult with the treating physician about the issues and risks so they can make an appropriate decision regarding your health and diving.
If cleared to dive, you should have an emergency action plan and a well-equipped medical kit that includes the required medications to avoid and treat an adrenal crisis.
— Leandra Lynn, AEMT
© Penyelam Siaga – Q2 2025
