science

Photosensitivity

Photosensitivity is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Photosensitivity rather than just read about it. In short: In medicine, photosensitivity is an abnormal reaction of the skin to light. There are two types: photoallergy and phototoxicity.

Key takeaways

Photosensitivity belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Photosensitivity to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Photosensitivity from memory before moving on to harder problems.

Reference excerpt

In medicine, photosensitivity is an abnormal reaction of the skin to light. There are two types: photoallergy and phototoxicity. The photosensitive ganglion cells in the mammalian eye are a separate class of light-detecting cells from the photoreceptor cells that function in vision.

Human medicine

Sensitivity of the skin to a light source can take various forms. People with particular skin types are more sensitive to sunburn. Particular medications make the skin more sensitive to sunlight; these include most of the tetracycline antibiotics, heart drugs amiodarone, and sulfonamides. Some dietary supplements, such as St. John's Wort, include photosensitivity as a possible side effect. Particular conditions lead to increased light sensitivity. Patients with systemic lupus erythematosus experience skin symptoms after sunlight exposure; some types of porphyria are aggravated by sunlight. A rare hereditary condition xeroderma pigmentosum (a defect in DNA repair) is thought to increase the risk of UV-light-exposure-related cancer by increasing photosensitivity.

Veterinary medicine

Photosensitivity occurs in multiple species including sheep, bovine, and horses. They are classified as primary if an ingested plant contains a photosensitive substance, like hypericin in St John's wort poisoning and ingestion of biserrula (Biserrula pelecinus) in sheep, or buckwheat plants (green or dried) in horses. In hepatogenous photosensitization, the photosensitzing substance is phylloerythrin, a normal end-product of chlorophyll metabolism. It accumulates in the body because of liver damage, reacts with UV light on the skin, and leads to free radical formation. These free radicals damage the skin, leading to ulceration, necrosis, and sloughing. Non-pigmented skin is most commonly affected.

See also Digital camera ISO Bergaptene Heliotropism Photophobia Solar urticaria Snow blindness Photosensitizer

Notes

External links

Sensor sensitivity (ISO) in digital cameras

Worked examples

Example 1 — a first encounter with Photosensitivity

Start with the simplest possible case. Write down what Photosensitivity claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Photosensitivity before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Photosensitivity ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Photosensitivity

In research: Photosensitivity appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Photosensitivity in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Photosensitivity is common in secondary-school and first-year university syllabi. It links to neighbouring topics Clinical pharmacology, Skin physiology, so understanding it makes those chapters shorter.
In everyday life: Look for Photosensitivity outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Photosensitivity in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Photosensitivity means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Photosensitivity out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Photosensitivity in simple terms?

In medicine, photosensitivity is an abnormal reaction of the skin to light. There are two types: photoallergy and phototoxicity.

Why does Photosensitivity matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Photosensitivity?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Photosensitivity.