Ocean
Watch
Monday, July 29, 1996
Stinging limu season is here;
try to steer clear
STINGING limu season is upon us. A few weeks ago, a
dermatologist told me he suspected this seaweed was the cause of a
blistering rash on the stomach of a girl swimming off the Waianae Coast.
Soon after, the state Health Department received reports of swimmers
afflicted with rashes from stinging limu along the Mokapu Peninsula,
Kailua Beach and Ewa.
People in Hawaii call a variety of marine organisms
stinging limu, but only one true seaweed is known to commonly cause a rash
in humans here. This blue-green seaweed, called Lyngbya majuscula (or
sometimes Microcoleus lyngbyaceus) usually grows in clumps, looking
like dark, matted masses of hair or felt. Most often this seaweed is
blackish-green or olive-green, but it also grows in shades of gray, red or
yellow.
The filaments of this seaweed grow up to 4 inches long,
often tangling with other seaweeds on reef flats, in tide pools or water
as deep as 100 feet. When loose in the water, this seaweed looks like
floating, tangled strands.
The toxicity of this seaweed varies greatly depending
upon region, season, and type. Not all strains of this seaweed are toxic.
WHEN toxic, stinging limu contains two potent,
inflammatory toxins, both causing skin damage upon contact. Typically,
seaweed fragments get caught inside swimsuits, rubbing these toxins into
the skin.
Epidemics of this seaweed-induced rash occasionally
occur in both Hawaii and Okinawa. In Hawaii, the highest number of cases
occur from June through September in windward swimming areas. Persistent
trade winds blowing during these summer months may dislodge the seaweed
from the bottom. Fragments then drift into swimming bays and beaches.
The Health Department issues public warnings when
outbreaks of this rash occur in swimmers. Heed these warnings. Common
areas are Kaneohe Bay, Kailua Bay and waters off Laie and Ewa, but the
seaweed grows and drifts in other areas too.
LIMITING swimming time in affected areas does not
guarantee protection, nor does the prompt removal of your bathing suit. If
you come in contact with the stinging variety of this stuff, you will
likely end up with a rash.
Rash victims feel an itching and burning sensation
minutes or even up to 24 hours after leaving the water. A red, sometimes
blistering rash occurs, sometimes in an entire swimsuit pattern. Most
surfers are all too familiar with this seaweed, which can wash down the
suit and irritate the most tender of body parts.
Such a rash also can occur on the face and in the eyes
and mouth. Some victims have swelling of eyes and mouth, but no rash.
For mild to moderate cases of skin rash, remove your
swimsuit immediately and wash skin vigorously with soap and water. Wash
the suit, too.
ALTHOUGH unproven, cool compresses or rubbing alcohol
may help relieve the pain. For persistent itching or skin rash, doctors
recommend trying 1 percent hydrocortisone ointment four times a day, and
one or two 25 milligram diphenhydramine (Benadryl) tablets every six
hours. These drugs are sold without prescription. Diphenhydramine may
cause drowsiness, so don't drive, swim, or surf after taking it.
Irrigate exposed eyes with tap water for at least 15
minutes. For severe discomfort, blistering not responding to first-aid
treatment, eye stings, or any signs of infection, see a doctor.
Any difficulty breathing signals an allergic reaction,
which is always a medical emergency.
Other marine organisms, including tiny jellyfish and
flatworm larvae, can cause similar-looking skin rashes. Distinguishing
these from this seaweed rash often is impossible.
The good news, however, is that treatment is the same.
