Most pollen questions Indians ask have city-specific answers, and many of those answers run against the common assumption that pollen season is one window in spring.
Below are the questions we get most often, grouped by theme. Sources at the bottom. If you want to check your own city's window, the India Pollen & Spore Calendar covers seven cities and the monsoon spore season.
The Basics
India has two pollen seasons. The spring peak (February–April) is driven by tree pollen: mulberry, neem, Holoptelea, Peltophorum. The post-monsoon peak (August–October) is dominated by weeds and grasses: Cannabis, Parthenium, Chenopodium, Poaceae. Most people are aware of one, not both.
No. Delhi has two sharp peaks and 94 recorded pollen types. Chandigarh has one of the highest single-species loads in any Indian city (Morus alba at ~67% of annual pollen). Bengaluru has near-year-round pollen due to its mild climate. Jaipur has a winter grass pollen peak, unusual among Indian cities. Chennai is shaped by two monsoon seasons.
Airborne pollen lands on nasal and eye membranes, triggering an IgE-mediated immune response. Symptoms include sneezing, runny nose, itchy eyes, and in more serious cases, asthma.
Estimates suggest 20–30% of Indians have allergic rhinitis, likely undercounted. In Bengaluru, a 1991 IISc study found 42.5% of respiratory allergy clinic patients tested positive for Parthenium alone.
City-Specific Questions
Two peaks. Spring (February–April): Morus alba (mulberry) accounts for ~34% of annual pollen. Autumn (August–October): Cannabis, Chenopodium, and Parthenium dominate. Delhi's chronic NO₂ and PM₂.₅ make pollen more allergenic than the same grain in cleaner air. This is covered in more detail under 'Why Allergies Are Getting Worse' below.
Bengaluru rarely gets a pollen-free window. Spring peak (February–May): Peltophorum and Prosopis juliflora. Parthenium persists through monsoon at low levels and peaks again in September–October. Run a HEPA purifier year-round, not just during peak months.
Morus alba accounts for ~66.7% of annual pollen load, among the highest single-species figures in any published Indian city study. Annual load exceeds 20,000 grains/m³. Primary peak: February–April. Secondary peak: September–October.
Yes. Prosopis juliflora (Mesquite) is a major year-round allergen, peaking February–May. Two monsoon seasons (southwest June–September, northeast October–November) shape both pollen suppression windows and fungal spore peaks.
Kolkata's intense monsoon keeps pollen counts lower than in drier northern cities. Spring tree pollen (March–May) is the primary pollen concern. But fungal spores are a major clinical burden: a 2019 study found 592 out of 742 allergy patients tested positive to at least one fungal extract. Kolkata's risk is as much spore-driven as pollen-driven.
The Monsoon & Fungal Spores
Largely yes for pollen. But it is not an allergy-free window. As humidity rises, fungal spore counts spike: particularly Cladosporium and Aspergillus fumigatus. If symptoms persist through July–August, spores are likely the cause, not pollen.
Cladosporium is the most abundant airborne genus in most Indian cities during monsoon. Aspergillus fumigatus is consistently the top allergen by skin prick test, especially in Kolkata. In semi-arid cities like Jaipur, Alternaria peaks in the drier post-monsoon period (October–December), not during the rains.
Heavy rain and wind rupture pollen grains and fungal spores into sub-micron particles that penetrate deep into the lower airways, far beyond where intact grains reach. Thunderstorms are common in India during pre-monsoon and monsoon transitions. Close windows immediately when a thunderstorm starts. This is why some people have their worst attacks on rainy days, not clear ones.
Why Allergies Are Getting Worse
Pollen count tells you how many grains are in the air, not how potent they are. As CO₂ rises, the same grain triggers a stronger immune response. Add Delhi's NO₂ and PM₂.₅ levels and the count becomes an even less complete picture of actual risk.
The pollen itself is becoming more potent. When CO₂ rises, plants produce more of their defence chemicals: the same proteins that trigger the immune system. At current CO₂ levels (~400 ppm), Parthenium's primary allergen (parthenin) is already 49% more potent than at mid-20th century levels. Same grain, hitting harder.
Yes. High NO₂ and ozone chemically modify pollen proteins through nitration, increasing IgE-binding. Pollen can also rupture into sub-2.5 μm particles that attach to PM₂.₅ soot and reach the lower respiratory tract. Symptoms can worsen even when pollen counts are not unusually high.
Yes. Introduced accidentally in 1956, it now covers 14+ million hectares across India. A single plant produces up to 624 million pollen grains. Active March–November, peaking August–October. Its allergen potency is increasing with rising CO₂.
What You Can Do
Run a HEPA purifier at night. Keep windows closed in the early morning when pollen peaks. Shower and change clothes when you return home: pollen sticks to hair and fabric and re-enters your indoor air.
Keep indoor humidity below 60%, where Aspergillus and Cladosporium growth slows. Use AC or a dehumidifier. Close windows immediately during thunderstorms. If you ventilate on calm days, do so midday rather than morning or evening.
Yes. An N95 captures most intact pollen grains and many sub-pollen particles. Wrap-around sunglasses reduce direct pollen contact with the eyes.
Yes. Sublingual immunotherapy (allergy drops or tablets) is now available in India for grass pollen, Parthenium, and other common allergens. It addresses the underlying cause, not just symptoms. If symptoms interfere with daily life, see an allergist rather than relying only on antihistamines.
Both are first-line treatments. Nasal corticosteroid sprays are generally more effective for nasal symptoms with regular use. Antihistamine eye drops help with eye symptoms. Neither addresses the underlying sensitisation.
This article is general information, not medical advice. If you have asthma, severe allergies, or persistent respiratory symptoms, consult a qualified allergist or pulmonologist.
Sources & Further Reading
PGIMER & Panjab University Chandigarh (Atmospheric Environment, 2021); Delhi aerobiological surveys (Singh & Babu 1982; Pandit & Dahiya, Grana, 2003); Bengaluru Parthenium sensitisation (Sriramarao et al., IISc, Clinical & Experimental Allergy, 1991); Chennai Mesquite study (Bhuvaneswari et al., Journal of Allergy and Clinical Immunology, 2004); Kolkata fungal spores (Dey et al., Aerobiologia, 2019); CO₂ effects on Parthenium (Bajwa et al., Pest Management Science, 2019; Rice, Wolf, Fleisher et al., Nature Plants, 2021).
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